The engine will probably be happiest with a 3.3 to a 3.55 ratio. That would still be comfortable for it in stoplight to stoplight traffic and give reasonable highway speed at a comfortable rpm.
This is something that may be simpler for many of us to do than tell you how to do it and what parts to use.
You still have to consider the same things I mentioned in post 8 and 11 last year.
lug bolt pattern= is it imperative that you stay with the same 6 bolt lug pattern?
That limits the supply of viable rear axles that are the proper width. Proper width meaning right at 62 inches for stock wheels with stock back spacing.
This chart is saying that 70/76 Chevy 4x4 rear axle should work if you can find a 3.55 rear end. If you aren't going to run reverse or wide wheels you can probably get away with a slightly wider rear axle. An early 70's 4x4 6 lug rear axle with 3.55 gears should run about 200 or less in most places.
http://www.quickperformance.com/Susp...nts_ep_44.html