Neither transmissions listed are a direct bolt in replacement.
The A833 is likely an easier and cheaper swap. The tricky part about this swap is that the part of the transmission that goes into the bellhousing, the front bearing retainer, is 5.125 inches, and the hole in the bellhousing is 4.686 inches. The front bearing retainer can be removed from the transmission and turned down on a lathe to fit the bellhousing. Cap head allen bolts will need to be used to reinstall the bearing retainer once it has been turned down. A new driveshaft will need to be made.
For an NV4500 swap, it is a little more complicated. NV4500 transmissions came in several different configurations... 2wd, 4wd, dodge, chevy...
The 1994-1997 Dodge 2wd transmission in my preference for the swap. Other versions of the NV4500 could likely be adapted but they bring about their own hurdles.
The 1994-1997 Dodge 2wd NV4500 can be made to work with a mechaniacal speedometer. The input shaft of the dodge transmission is 1 inch longer than the input shaft of the gm transmissions. This allows you to bolt the transmission up to the bellhousing by using a 1 inch adapter plate. Advance Adapters sells an adapter plate that will let you do that, almost. Again the Adapter plate is set up to go in a bellhousing with a 5.125 hole, and the 48 bellhousing has a smaller 4.686 hole. Either the bellhousing will need to be bored out to fit the adapter plate, or the adapter plate will need to be turned down to fit the bellhousing.
If you do a search of my screen name and NV4500, you will likely find dozens of posts which go into further detail of the NV4500 swap.
