70 Jeepster Commando gearing

I have 70 Commando with the original Buick 225 V6, a 3 speed manual tranny and I think a Dana 20 xfer case. After finally getting it running, I definately don't have enough gearing for trail use. It has the original Dana 27 front and Dana 44 rear axles w/ 3.73:1 gears with some old school Ridgerunner 11.5x15 tires. Now, of course the first thing anybody might say is change the axle gears. I will do this with my Scout II running gear, but not yet. The axles that are in it are what I consider throw-away. I am going to build the Scout II (sorry Jeep purists) axles with all the goodies and 4.88 gearing, but with budget allowance. Here's my question: What transmission options have I got for a direct bolt in replacement for a lower first gear. I don't want to buy a tranny and then have to pay another $400 or more for adapters. I can handle driveshaft mods if needed, even custom crossmembers.