500 cfm edelbrock carburetor...

You can spend a lot of time fiddling with carb jets & rods and pulling plugs to guess at O/F ratio, because you are flying blind. Next time you have your exhaust pipe down, weld an O2 bung in it as close to the manifold as possible. Anybody doing exhaust work should do this. You can install a plug until needed. You can get a small "rich/lean" box from Holley or MSD to use with any 3-wire O2 sensor. I got several for ~$25 off ebay, one was even new ($175 retail). Even better is wideband O2, but you might pay $100 used ($300 retail). Any muffler shop can quickly weld a bung in (use 3/4 hole saw). I even managed with my $90 Harbor Freight welder.