Please help with Tire offset

Hi everyone

Another question

We installed a b body BB rear end from the late 60,s in our 1971 Demon when we did the measurements this is what we found

From the front of the drum to the lip of the rim we have 3 x 3/4 inches

My question is what offset should I use

We tried a rim off a 2007 Dodge Magnum RT it looked like it would need to roll the lip

Im thinking about trying to find an 8 1/4 rear end