i bought the truck with the engine in it with the new 750 holley on it tried to tune the holley ,it needed rejetted it ran rich as can be primary jet size was too big so i installed a 600 edlebrock 1406 ran a little on the lean side though(no jet or metering rod changes just out of the box). i put the 750 on craigslist and ended up trading for a brand new 1405 and a trick kit the edelbrock was set up for a 355 with an a/f meter so i haven't had to change jets or metering rods, now as far as driveability as far as cam change is concerned with the 12-246-3 cam and holley 750 it just wanted to make power in all the wrong places even with the edelbrock 600s gas milage went from 6-9 and that's it it was just as fast as it is now even with a slightly smaller cam.the 12-246-3 makes peak torque at 3900 rpm and peak hp at 5900 rpm so this isn't a drag truck its my dd with the 12-235-2 im getting 12 city 14 highway and the idle is better the torque comes in at lower rpm the truck just seems to drive a lot better on the street it dosent want to be at such a high rpm. now if it wasn't my dd and was a 2wd 1/2 ton with 4;10 gears that cam and a 750 with a single plane intake that would run awesome but not a 3/4 ton 4x4 with 33s and 4:10 gears just my opinion
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