Ross - if it's the original rear end, they were most commonly 3.90 .... clean it up good, check the pinion seal, redo the cover with some RTV silicone on it, and unless it's got some holes in it, it won't leak .... for awhile
the stock rear can handle V8's fine, a buddy of mine has been abuseing one with
a 427 with no problems, just make sure the pinion bearing/seal are ok, which is the place it may be leaking
Bill
