8 1/4 diff with 2.45 gears

Woody'sScamp said
I'm thinking of going the "new" route also. My car is a '75 318 Scamp with an open 2.45's. The only upgrades so far are a 4bbl and dual exhaust with the stock manifolds. I've read all these threads about upgrading 8 1/4's and I'm still confused, probably because I'm in uncharted territory!
1. If I buy a new sure grip carrier and new ring and pinion gears am I good to go? (I found a Mopar Performance 8 1/4 sure grip on Summit or Jegs for $386.) I'm looking at 3.21 or 3.55 gears.
2. Thinking about 3.21 gears, more highway than city driving. I did not find any 3.23 gears for an 8 1/4 read end, only 3.21's. Were 3.23's for early years than 1975?
3. My rear end is offset, can this be done? My rear end is off the car now so this may be the time to do it. Thanks in advance for the help.
Woody

View attachment 1715189231

1. 3.21's are a great all around gear especially for me since I have a A999 (wide ratio gears) transmission so it does have a decent getup and go.
2. 3.23 gears I believe are not an option in 8 1/4's. They are in 8 3/4's and Dana's. I just came back from a round trip drive to Louisville CO, from Utah (500+ miles one way) I have 245/60R15's in the back and at 3,000 rpms I was cruisin' about 72 mph. Mileage ranged from 14.6 (50 mph crosswinds + uphill) to 17.4 mpg's. With the previous tires (255/60R15's), I was going 74mph at 3,000 rpms. Also I converted the A999 to non-lockup (I did this so I didn't have to shell out a lot of cash for a high performance high stall LU TQ-convertor)
3. Offset? Since the rear is is off the car I'd say yes. But keep in mind once you take all the guts out and re-install everything with the near gears you have to set the preload, do the correct ring/pinion alignment with shims, etc... My knowledge of these rears is moderate at best, I did attempt to do all this once I gave up after a week, I got close according to the local gear shop, even then it still made noise.