Under $4k budget build LA360 build

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Sounds like you are well on your way!
What your 3 things add up to is pretty much personal choice. What does your engine builder suggest? Carbs are pretty much a personal thing; I'm a Holley guy myself but to each his own. And a carb swap can be easily done if you're not happy with the results. What does your engine guy say about the TC and pistons?

The machinist I was talking to turned out be someone I wouldn’t trust to make any decisions for me. He’s a quality guy who works with stock setups and doesn’t dip into the performance world. The block was measured and is said to be ready for assembly. After I get the pistons sorted out, I’m going take it to another shop that was recommended to get the rotating assembly balanced and a final assessment on the block and get an accurate measurement of the heads combustion chambers... I did my own measurements(twice now) and got about 71cc’s, but I want to make sure. They’re going to Sonic check it and we’ll see what else they suggest. I trust the knowledge here on this site on piston choice and anything else MOPAR related, so I figured I’d have my setup dialed in as best as I can before going to the new machinist.
 
Bummer. Has the block already been bored .040 over? if so, then the choice of pistons will depend on whether you want the lightest piston available (hypereutectic) or the strongest (forged) along with cam/compression compatibility and profile (domed, flat top, cut for valve reliefs, etc). Just me again, but I wouldn't be shopping around for used piston no matter the condition; when I chose mine I did so by availability and cost and did a side-by-side comparison, as by choosing I boxed myself in to a set of .030 pistons and had to have my std block re-bored.
 
Bummer. Has the block already been bored .040 over? if so, then the choice of pistons will depend on whether you want the lightest piston available (hypereutectic) or the strongest (forged) along with cam/compression compatibility and profile (domed, flat top, cut for valve reliefs, etc). Just me again, but I wouldn't be shopping around for used piston no matter the condition; when I chose mine I did so by availability and cost and did a side-by-side comparison, as by choosing I boxed myself in to a set of .030 pistons and had to have my std block re-bored.

The previous owner had the block prepped be a machine shop, which included the .040 over bore. My main concern is finding a piston that will work with my goals and current collection of parts. I’d change the cam if necessary though. I got a good deal on it and would break even if I went another direction and wanted to sell it and lifters. I want forged pistons, but don’t want to fork over the big bucks, so I was considering used.
 
I’ve been collecting parts and I’m getting close. The last big items I need are .040 pistons, torque converter(3000 recommended with my cam) and carb(I’m leaning towards the Edlebrock 1407... 750cfm). I installed my 8 3/4 rear end, but stayed with the 3.23 gears while deciding on a final gear ratio(It’s what was already in there)... Since then, I’ve decided to go with 3.91 gears.

I can purchase a set of lightly used -5cc Probe flat top forged pistons. The advertised compression is around 9.5:1 with my head combo, but when I put it in the calculator it shows 10.5:1 static and 8.8:1 dynamic, which is too high for my use. I would need to put a huge cam in to get the dynamic to a pump gas friendly range. The KB 107’s seem like a good fit for my setup. I’m still trying to figure out the best combo for quench and dynamic compression. I’d like to stay below 10:1scr and 8:1 dynamic and under .40 quench.

Part that I have

RPM Air Gap Intake (waiting on confirmation from seller)
Stock 974 iron heads with multi angle value job and 2.02/1.60 valves(no machine work yet)
273 adjustable rocker arms shaft and push rods
Bushed 340 rods newly machined with new new ARP bolts
Stock cast 3.58 crank
7177 Edlebrock Cam and lifters 234/244 @.50
.488/.510 lift 112 lobe separation 107 center
Double roller timing chain
High volume oil pump and pickup
Stock oil pan(may upgrade)
Oil pump drive
Mechanical fuel pump
MSD 6a ignition, distributor and blaster 2 coil
E3 spark plugs
TTI headers
904 transmission

Parts I Need help deciding on

.040 Pistons
Carburetor
Torque Converter

Any suggestions would be appreciated. Thank you for the articles, posts and help I’ve gotten so far!
I'd run those gears first you might like them I had 391 then went 355 and love them they are perfect and droped damn near a half second in the quarter mile .
 
Nice! @A/JForms broke it down and after I looked into it more and started to understand the relationships better, the bigger 3.91 gears make sense for my use.
 
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