I beleive the Predator has two sliding dewhickies that make it a "variabe venturi" carb--they only slide open as far as the engine can suck them open,which makes it a "universal" carb that'll work on just about any cubic inch engine..
I had a 235 straight six in a '56 Chevy 3200 series truck that had a pretty large one barrel Rochester carb on it factory--the thing always ran good,but it sucked gas down pretty bad for a 6 banger...when I decided to rebuild the carb after the accelerator pump started dying,I learned it was also used on some later V6 engines ,like the 401 used in big C-60 sized trucks!...might have been jetted differently,but I often wondered if my carb was one off one of those,it only gave 10-12 mpg on a good day...(low rear end gears probably didn't help much either)..
I tried swapping a 600 CFM Edelbrock onto a 250 six in a '79 C-10 I had,that had a crappy Rochester "Vari-Jet" 2 bbl carb that always ran like dog crap,it would idle rough,stuble and spit back under acceleration,and seemed to starve on the smaller primary barrel for fuel,and be too rich when the secondary opened--GM made it by sawing a Q-jet in half,and they never seemed to work all that great...
I made a home brewed manifold adapter to put the Edelbrock on the 2 bbl integral intake,the "prototype" I made of 3/4" plywood!--and I actually drove the truck several miles with that to see if it would be worth doing---it actually ran decent,so I had a guy at a machine shop I know mill me one out of a slab of aluminum..I later found out the 250 didn't like the secondaries,it would bog when you booted it,the amount of air the carb would let in actually caused the velocity of the incoming fuel/air mixture get so low it just laid an egg..I removed the linkage that opened the secondaries,effectively making it a 2 bbl carb,and it ran great that way for almost a year...eventuall the #6 piston failed,preignition from the original lean running carb had caused the top ring groove to break,exposing the top ring,and that was the end of that engine..ended up putting a 305 in it after that,and the Edelbrock worked fine on that with all 4 barrels !...I still have the home brewed carb adapter for the 250 though...I heard some Jeeps and Citations with 2.8's used the same Vari-Jet carb..
