Disc Brake Hold Off & Prop Valves

Um........ adjust the carb?
Your carb has 4 or 5 major fuel delivery circuits; so you need to be a lil more specific as to under what circumstances it is lean.
Your carb is a speed/density device. It reacts to rpm and load.
If it's running lean, that means it's moving air, which is a good thing. Your job is to make sure as best as you can, to make sure that air has the right amount of fuel in it.
The circuits are;
the Low-Speed, which is the Idle and Transfer Slots
the WOT (Wide Open Throttle), which is the MJs together with the PV (PowerValve or Power System)
the Part Throttle, which is principally the Primary MJ.
It is important to remember that as the throttle is opened, and each subsequent system comes on line, NONE of the other systems actually shut off. This means that as your rpm is screaming thru the Torque peak at WOT, the idle system and the transferSlots are still supplying some fuel, together with the Mainjets and the Power System.
On Holley-type carbs the Idle Circuit is comprised of FIVE parts, namely;
the Fuel level, the Idle-air bleeds, the low-speed circuit, and the mixture screws together with a small amount coming from the transfer slots.
The hardest system to adjust right, is this Idle-System, so let's start there.
If your engine seems to be lean at idle, and you are experiencing a tip-in sag or hesitation; I can almost guarantee you that your transfers are NOT flowing enough or Not flowing at all. If this is true, I can almost guarantee you that you are running too much Idle spark-advance.
While it's true that the 292 cam likes a lot of spark-advance, it is JUST as true that the 318 cam likes lots of spark advance. The problem is that with increased IDLE spark-advance, comes increased Idle-rpm. Which causes you to to close the throttle, but that action simultaneously shuts off BOTH air and fuel. So you can only reduce the throttle so far and then the transfer slots get shut off. You can make the engine still idle, by opening the mixture screws but eventually they top out at max flow. But you can make it idle this way.
But two things happen when the Idle is fudged up this way;
1) almost invariably the transfers stop flowing, so when you step on the gas at idle, it takes a bit of time for the circuit to come back on line, during which the AFR goes horribly lean, and then you get a lean tip-in stumble. and
2) as soon as you get past the stumble, the AFR goes very rich because the mixture screws are wound out all the way.
And the reason for this monkey-business is the excessive Idle spark-advance.

The increased spark advance is sometimes/ usually nice to have because the very low-rpm power goes up, making the engine both more responsive and peppier and that makes it more fun to drive. But getting off-idle advance by cranking the Idle-advance up, is NOT the answer.

So, if you have done this, you gotta undo it.
Start here;
remove the carb and set the transfer slot exposure underneath the Primary throttle blades to a little taller than wide; enough so that you can just see it. Reset the mixture screws to, in the center of their working range, which on a Holley type is no more than one turn out from lightly seated. I think all metering-rod carbs are about 2.5 turns out. CLOSE the Secondaries up tight but not sticking.
Make sure your Vcan is connected to a ported vacuum source, for now.
Make sure you have a PCV installed and plumbed correctly which is to the underside of the primary throttle blades.
Make sure your brake-Booster is dead-headed at the diaphragm, that is to say, not sucking air continuously.
Make sure that the intake is sealed to the intake ports.
Make sure that the carb is sealed to the pad.
Make sure that ALL vacuum devices that may be bolted to the intake, are functioning as designed.
Make sure your exhaust is flowing freely. I assume that you have headers, cuz that cam demands them. And it also demands the heat-crossover be defeated *1
Make sure your valve lash, if any, is on the loose side. *2
Make sure that if you are running Hydraulic lifters, that the preload is on or close to the minimum adjustment.*2
Make sure your ring gaps are adequate, that the rings don't drag your idle-speed down as the engine comes up to temp.*3
Make sure your engine temp is at least 180* and is stable.*4
As always, make sure your WET fuel-level is constant.
Ok then;
Bolt the carb back on and start her up. you will immediately notice the higher idle-speed; do not touch the Curb-Idle speed screw! After she warms up, back off the timing to get the rpm that you want. This is your starting point. From here you need to fine tune it just a lil for your particular combination of parts.

Each of the circuits have different ways to be adjusted. On some circuits the air can be trimmed as well as the fuel.
At WOT, you need to adjust the mainjets
At Idle, the transfer slots to idle circuit balance, and trimmed by the mixture screws.
At Part Throttle, mostly the Primary MJ, but includes the PV opening point .
But no matter what you do, the very FIRST adjustment is always the Fuel Level.

Happy HotRodding.

*1 If you don't block the cross over, then during the end of the exhaust cycle, with headers, when the negative exhaust pulse is supposed to be helping the exhaust out and the new fresh A/F charge into the cylinder, the signal gets lost in the passage and out the other side. This happens to the center FOUR cylinders. This robes your engine of a lot of power potential. I'll guess a full cam size worth of power.
*2, if the valves do not seat properly; firstly, they run hot, but secondly max cylinder pressure is not achieved, and thirdly, the overlap period gets screwed up. Loose is better than tight, but hydraulics should Not be clacking.
*3 tight rings put a tremendous amount of heat into the cylinder walls but also require a lot of horsepower to drag up and down. Too tight and they can tear the tops of the pistons right off.
*4, DO NOT BOTHER trying to tune an engine in the which the idle coolant temperature is all over the place. If it varies more than 10* fix it! The thermostat sets the MINIMUM coolant temperature, and that is all it does or should I say, that is all it is supposed to do,lol. If you have alloy heads, I suggest trying to run them a lil hotter; I have been running mine at 207* since 1999. Alloy heads suck heat out of the chambers very well, to the point that your engine needs the equivalent of about a half to a full point more Static Compression Ratio just to break even (to iron heads) on the Power Delivery. Whereas with iron, your pressure is limited to about 160/165psi for use with pumpgas, you can run at least 20/25psi more with Alloy heads, and you sorta need to, to compensate for the loss of chamber heat at WOT.