Holley sniper works great. Took it some time to learn how to go into gear and not stall out, and I had to play with the IAC settings a bit but it's working perfectly for me.

Were you able to get the IAC% down to a reasonable number? I’m still playing with mine but getting down to that target number has been a challenge. Jeff Harris said that was pretty typical on a generic Facebook post I posted asking about it.

fbc - 3 circuit. I have not had the blocks off to answer your other questions. Played with it this afternoon. My mixture screws are about 1-3/8 out and I opened the secondaries up and closed the primaries to try to get better parity between front and back. I just can’t seem to get more that 8-9 inches of vacuum at about 950rpm..... going to drop it off lift and try it tomorrow.

i truly don’t think you can see any of the transfer slot with the throttle closed.....

Yeah it'll sit around 5% at idle (750rpm) and go to around 30%, depending on temperature, when in gear. At first it would stumble when dogging into forward or reverse but a combination of it learning and playing with the IAC settings it's perfect now. Fires right up every time no matter what.

I have a similar setup with a much bigger cam with a 1000cfm 4150 and it runs like EFI. I adjusted my secondaries to be 80% of the primaries. It is critical that the butterflies stay within the transfer slot. You should be able to maintain that. I also adjust all 4 corners the same . With a good multi-spark ignition too much fuel is less of a problem than too little. Without some type of timing control for idle you will need to keep your neutral idle speed around 900-950 to get a decent idle in gear. I have the Daytona Sensors CD-1 ignition which is programmable and it also has idle control. I have the ignition ramp up the timing if the idle speed drops to keep it running smooth while docking. What's your compression, 32 degrees sounds kind of light for a BBC? I have 10.1:1 and run 36 degrees on pump 93.

Is the OP’s Dominator 3 circuit ? I ask for on going study of 2 vs 3 circuit Dom’s and continually notice 2 circuits have less tuning issues than 3’s, including stock and modified carbs.