Ever since I put in the T-5 and modern rear end it started using more gas so I went to the junkyard and grabbed the jet and power valve spring from a 60 wagon with a 235/powerglide. It had a 42 jet which was a little too small and I did find another carb in the shed and it had a 51 jet and its in and seems to be working just fine,I hope I can get some more driving in before the snow flies so I can get a reading off the plugs and see if the gas consumption goes down. It has 2.79 gears and probably is a little too tall but with the T-5 from a 2.8 it gets out of its way just fine and does not do too bad and I cant use 5th much but its alot better then with the original trans and rear end.

Running it too low in rpms is just as bad as running it too high. I would gear it to be running about 2000-2300 rpms at 65mph.

Also, make sure your speedometer is accurate. It's unlikely to be correct after a significant gear change like that.

The speedo is way off right now and I am not going to fix it untill I decide on the gear I want,right now with the 2.79 gears it does fine if I dont use 5th and I was wanting to put 3.25 or 3.50 gears. I am going to install a tach and a vacumn gauge to see how fast or slow the motor is spinning.