Ok i took my camaro for its first long highway drive today, since a 383 engine swap. Its 10:1 Compression with a edelbrock .488/.510 cam, edelbrock 7101 intake and holley 4150hp 750CFM Double Pumper Carb. The carb is straight out of the box and is running a little rich so i know that is hurting my MPG a little. Behind all of this is a t-5 with a hurst shifter. IDK why but i cant get the transmission to shift into 5th gear, with the hurst shifter. i dont know how the stock shifter did because i never drove the car with the stock shifter. But with my 3.42 gears in the RE and in 4th gear i managed about 15 mpg coming 65 or so miles to school, cruzing at about 3500 rpm the whole way. What do u guys think my MPG will go to when i get her into 5th gear @ about 2150 RPM? Can i see 20 MPG highway with 5th gear and a correctly tuned carb?

 

Maybe 17-18. I don't think 20 is impossible but unlikely with a 750 DP.
For my sake, I hope it is though! I am just finishing my 383 swap. I'm trying it with a 650DP though. I'd rather have a 750, but I'm hoping the 650 is enough. The carb was originally destined for a 350 rebuild, but not anymore.