holley 670 street avenger jetting questions

Anyone have experience with the avenger series of carbs?

not on a mopar but looking for advice. ford 351 Cleveland 4 barrel heads (which essentially have big block sized ports) cams like 550 lift, eddy intake i forget which one exactly. Basically just simple bolt ons. It sat for a while but got started occasionally and moved around a few times and ran great every time. Finally got it back on the road and my father bought a brand new 670 street avenger for it bolted it on. It starts up and cruises down the road fine, But this car is seriously down on power. Hitting on all 8 wires in the correct order, timing is around 12-14 initial 36 total all in around 2k rpm. It just doesn't have half the power it should.

Now after that I bought a 670 street avenger for my 302, roller cam motor with intake cam and exhaust. nothing too wild but has a nice lope. Now this car I have an air fuel gauge in, the carb runs pretty good all around but when you have it floored it runs about a 13.5-1 air fuel ratio. Keep in mind this carb is recommended for 300-400 hp at best this motor makes 300hp and is on the small side as far as cubic inches are concerned.

In short I am thinking the carb is pretty darn lean out of the box and think I need to jet up on the 351 to solve the no power issue. Anyone else have similar issues with a street avenger?