Rearend info help

If I switched wm out I'd split the difference between what you have and what you claim to want.... Either 2.94 or maybe a 3.07, which was used in alot of newer 8-1/4 applications. Definitely available aftermarket. I probably wouldn't go higher (numerically) than 3.21/3.23
I've had a few vehicles with 2.94 including 2 ex squad diplomats and an 87 B250 van and that's really a decent all around gear set
I've also had 3.55s in a few, the only one I recall w/I overdrive was an 83 D250 but it had tall (235/85-16) tires.