Ah, gotcha, I wasn't sure which it had OE. Yes, the Hurricane 134F is the F head version of the old flat head Go Devil (134L). The Dauntless 225 is a phenomenal engine and would be a great swap for you while still keeping it period correct. I'd steer clear of a new jeep drivetrain swap purely for complexity and computer/wiring hassle as well as the fact that I like vintage stuff. Just my .02 but your mileage may vary. As for period swaps, Ford 289's and Chev 327's were really common, as were pinto 4 cyl's but I never cared for those. I always thought a flathead V8 would be cool in one. Studebaker flathead 6's will bolt up to the original T90 behind a 134, and I believe the Super Hurricane too.
That's just a few options, I'm happy to help with anything I can, Willys are kinda my thing.