Switching to Rallys - need help

[thebabybrahma]

My 72 has 15x6 Weld wheels on the front and 15x10 on the rear wearing 225/75 and 315/75 tires. I want to put on some Rallys. My trouble is the truck has been set up to be level or close to it with the above tires. I have some Rallys with 255/70s on them, but the front end sits about 1 1/2" higher in the front with the 255s on it.
What size tire can I run in the front to get it back level or some rake? thought about 235 or 245/ 60 and stay with a 255 in the rear.
Or do I need to lower the front of the truck more to accomodate a 255 (maybe a 60 series) in the front?
Attached is a picture of the truck with the little fronts and big rears...