I have a 496 with a Blower Shop 250 w/7 psi currently running a 1000 HP Pro Systems carb. My cfms are limited by the carb size. I can only reach 5100 rpms @ 6 psi. Boat runs 80 on gps. (The engine dynoed at 600 w/o any s/c on it.) If I did my calculations correctly I need just under 1300 cfms. I am looking at the Holley Terminator Stealth X kit. They offer a 4500 TB flowing 1440 cfms or a dual 4150 TB system flowing 1900 cfms. The single would be nice for the easier linkage, fuel system, and space under the hatch. I am new to EFI and wasn't sure if the fuel distribution is still better with dual throttle bodies over one? Thanks in advance!

Duals are better. You should measure vacuum under your carb. A huge dominator would be an easy solution. No 4150 based carb will have enough area to not be a restriction on that combo

yes, a single carb or injected tb in middle will have horrible distribution. I dynoed a 454 w bm 420 w dual 4bbls. it had great distribution and actually had good BSFCS