Inspection of a 904 torqueflite
The low gear sets are easy to find. ANY V6 auto Dakota, Durango, Ram 1500, or 1500 Van, or XJ Cherokee or other Jeep that used the 42RH or 42RE (A500). Also Diplomats, 5th Avenues, etc... Basically anything that used a 904 based transmission after 1980 or so. If the pan shape is the same as yours it's A904 based.
The ATSG manual makes a couple assumptions. First, they assume you know how to disassemble and reassemble a transmission. Second, they somewhat assume you will be replacing standard wearing items and anything else that appears worn or damaged. There is also an assumption that you have the tools and ability to accurately measure clearances.
In my experience the internal bushings probably don't need replacing, but thrust washers generally do. If I buy a kit before I disassemble, I but the master kit with the bushings. If I don't need to change the bushings, I don't. New clutch friction and steel plates and thrust washers will usually get things reasonably close (as close to spec as it may have been when it left the factory perhaps).
I mentioned Transtar because they have retail locations in most cities. Why buy on line if you can support a local business? Also, if you need any other components like selective spacers or maybe a used low gear set, they just might have one on hand. Pretty good chance the fellow behind the counter is a car guy who knows from transmissions.