No brainer-SM 465. Bolts to the stock 327 bell and has the thinest adapter plate available giving you the longest rear driveshaft. An SM420 would also work but parts are getting a little tougher to find, there is more of a front driveshaft clearence problem, and the adapters are longer-it is somewhat lighter. Check Novak's site for the various options. You will have to modify both driveshafts, floor pan/transmission cover, and the cross member but lots of threads on that in several forums.
1955 CJ 3B, 381" sbc, AGE M22W, Teralows, Warn OD, OBA, Premier Power welder, Warn 8274
1968 CJ 5, factory 225" w/ headers/450 cfm Holley, T86AA, Belleview winch, Warn OD
2012 Wrangler Rubicon Unlimited, Warn 9.5 xp-s winch