you will want a 90 or earlier AOD which is all mechanical, no computer required.
new torque convertor
the adapter for the aod runs about 600.00
you will need to shorten the rear drive line and the front will need to be longer by about an inch and a half.
the transmission is a bit wider so some exhaust modification will be necessary. the shift linkage should still work ok. but will need adjusting and possibly lengthening
you will need a lokar t-v cable.
if you have a j shift dana 20 you will have to twin stick it.
you will need a new flexplate that is 164 tooth and 28 oz imbalance, and a new starter to match.
so there are lots of things to do. it is not all that hard to do, if you have the desire. I put one in a 67 mustang. a lot of the same changes are required. but it does take time and if you don't want to do the work yourself, you are going to have to pay for it. and if the place you are going has not done it several times before, it is going to take them time to research it and figure out all the little tips and tricks that go into this kind of conversion.
yeah that's a lot of money, but there is more to it than simply swapping transmissions.