I hope to be doing the same thing to my 85. the poor old 22re is just tired. even with gearing, 37's are just a bit too much. ive had a plan to swap in a 3.4, just never got around to it. but now, the old motor is barely running, and I may be forced to swap it in sooner.
it will still be a little while yet, ive got a few more projects I would like to get done.
like you, I will probably just run the chain driven case at first, then eventually swapping in duals. it just depends on what all I find for a donor/swap rig.