Bellhousing cast to case of transmission is the NV3500.
The NV4500 is a fairly straight forward swap. Shifter location is about 5.5 inches back of where an sm420 shift tower is. I use the 1994-1997 Dodge 2wd version in stovebolts. This transmission will bolt up with an adapter plate, and can be made to work with a Mechanical speedometer.
The Gm version of the NV4500 has no provisions to run a mechanical speedometer.
Advance Adapter sells an adapter plate that almost bolts to a stovebolt bellhousing. I say almost because the bolt pattern is correct, but the indexing hole is too large. Most stovebolts before 1967 have a bellhousing that is indexed to 4.686 inches. The AA plate is indexed to 5.125 inches. Either the indexing lip on the adapter plate will need to be turned down to 4.683 inches, or the bellhousing will need to be bored out to 5.125 inches.
If you get the dodge standard duty imput shaft, it is 10 spline on 1 1/8, just like a stovebolt clutch. If you get the heavy duty dodge version (diesel) it is 10 spline on 1 1/4 shaft. The shaft can be swapped out without getting into the transmission.
Both the heavy duty bearing retainer and the standard duty dodge bearing retainers are to big to fit in a gm throwout bearing. I took the standard duty bearing retainer, and spun it down on a lathe to match the sm 420 bearing retainer snout. About .060 needed to be removed... take your own measurements as I don't remember the exact numbers.
So the 94-97 dodge version can be mated to a stovebolt with an adapter plate, and most of the stock clutch components can be used. It is likely a custom pilot bearing/bushing will need to be made. The tip of the sm420 and many other gm transmissions is 0.590 inches. The dodge NV4500 has a tip of 0.750 inches. I just bore out a bronze oilite bushing to the desired size.
As far as gear ratios... the NV4500 from 1-4 lines up pretty closely with an sm420. The sm420 has a lower first gear ratio of 7.05:1 compared to 5.61:1 of the dodge NV4500. The NV4500 has a 0.73:1 5th or OD gear. The NV4500 is a popular swap in jeeps, land cruisers, fords, and gm wheelers, espeacially when it is used with a low ratio transfer caselike an Atlas. With 4.11 gears, and a 4:1 reduction in the transfer case, it is possible to achieve a crawl ratio of about 92:1. Of course that could be 115:1 or lower with 5.14 gears.
The NV4500 is a heavy transmission. It weighs in around 200 lbs dry. An sm420 is closer to 130 lbs.
