I’m almost positive the rear end already has 3.23. I’m learning that going with a 2000 stall when having the transmission rebuilt was possibly a mistake.
2000 stall is stock would work with a mild cam, but a mild cam might be too much with your possible cr to run on pump gas, meaning you might need to run a fair size cam which will want more stall and gears.
Even a fairly mild cam would benefit more stall and gears in a 318.