Diesel Bombers - 46 Dodge 5.9 rat rod build... transmission?!?!

Hey everyone, I'm new here, and new to diesels to please bare with me. I've done some searching for weeks and can't seem to find real answers.
I've got a 46 dodge truck I am building into a rat rod. I have just had a 5.9 Cummins out of a Thomas School bus basically fall into my possession. It's out of between a 94-98 so it's the 12v. Problem being is the trans. It has an Allison 643 attached to it Ridiculously big and heavy trans which isn't even the big problem, big problem is the 1.0 final drive in 4th gear. With a nice 4.10 rear end I am looking at 56mph at 2600rpm. Not an option. I want to be able to drive this thing around, and to shows and not revving it out the whole time. It's goning to be 2wd, 22" rear wheel with about 30" tire. Will NOT be towing anything.
So here is what I have looked at:
Gear Vendor... $3000 for an overdrive setup... way out of my budget for a rat rod build
Change the trans... Allison 1000 would be great but I have no electronics with this engine so how could that work?
nv4500... other then expense, I've talked to a lot of people who say it shifts weird, and doesn't handle power or race/fast/ shifting.
47RH... I have heard they don't hold up well either, and I imagine being hydraulic, it should work with my mechanic/ non computer controlled engine right??
As stated I am not towing anything ever, I'm not drag racing this thing but don't plan on sitting back letting someone try and pass me. I am open still to rear end gears, planning on building a 9" And I don't plan on doing 150mph but at least 100mph would be nice. Any ideas, help, donations?