Rebuild on 300 Cummins

Truck, just needs some longer legs, now. 4:44’s under it and would like to stay with IH rear ends but not sure what they offered from the 3:73 - 3:90ish range? ‘77 4070B.

 

My 77 4200 had 4:63’s under it. With a 8V92TA / 13 spd about 70 was about all she had comfortably….

 

About 67, is enough right rpm’s out of this truck, with a 13 OD.

 

International had weird gear ratios, 3:91, 4:10 etc.
The truck in my profile pic was a '77. 350 Big Cam 1, 13 over with 4:10's, If I wound it up, higher 70's
It was good for what I was doing at the time (55 mph speed limit then).
You probably have the International RA355 rears in it. That's the model number not the ratio.

I also ran a 1987 International with a 425 Cat 3406B, 13 over with 3:91 rears. That one topped out at 87 mph.
Both trucks were on 11R/22.5 rubber.

 

Well, looks like I need a set of 4:10’s or 3:91’s. Transmission is a 1250 and more than likely, the original. Not sure, which rears would be more suitable for this engine and transmission? Engine is flirting with 400hp.