GM 205 is a pretty big case for an 81" wheelbase. especially if you are adding a new trans since most everything out there is longer than a T-90.
If it were me I'd swap to a petronics solid state distributer, better plugs/wires/coil, and if you still need more, add a Warn/Saturn overdrive and run with it. If its just going to be a hunting rig, you can't really beat what the army designed it with. On top of that, its only going up in value, and if you swap it all out, your just gonna lose money in the long run. If its really a builder you are looking for, then you are better off starting with a CJ-7 or YJ because you'll be miles ahead by the time you swap everything out of your M. I run a '53 M38-A1 stock, including 24 volt electrics and have for about 11 years and I have yet to find anything that I can't go up that I have wanted to with a bit of decent driving. I've run 4+ trails in Moab with it open on both ends with no prob. Spaggyroe can attest to that. I'm not saying that I'm an amazing driver, just that folks have taken these old goats anywhere and everywhere for over 60 years in stock form, so you really need to ask what your really after. Anyway, sorry for the rant, just really belive in these old beasts, and hate to see them hacked up and lose the history forever. On the other hand, do what you want, it makes mine worth more....