If you want a gut check of what you will eventually get into, download the updated ASTG E4OD Manuals and the Transgo E4OD upgrade manual which can be easily sourced online. If you are comfortable with the technical stuff in the manuals then I would suggest that when you get a truck, search the wrecking yards, CL or FB for a '96-'97 trans as these are the best place to start a rebuild otherwise you need to add additional upgraded internals that these have. Then use a good parts company to order a quality kit and TC from and enjoy a week or so with your new toy. After you swap in your fresh rebuild put your takeout back up for sale to recover your initial cost of the trans. There's also lots of rebuild threads scattered throughout the various ford truck and bronco forums, not everything is applicable but you'll get the idea. I believe Racer X had a good tear down/rebuild article on their site that gave lots of pictures and details and reasons why, it was called "E4OD High Performance Rebuild." Probably can find that on the interwebs somewhere if they don't have it up still.
If the truck shifts ok for now get a temp gauge and watch it, that's your earliest indicator. Put a pressure gauge on the port and check the shift pressures against the manual. Also put a 6.0 cooler and lines/trans fittings from the 5r110. Put a filter in the cooling loop and run it till it starts to go. You'll likely get 100-125k out of the original trans but after that it's usually running on borrowed time.
I originally planned to have BTS do mine but their back log was too long for my time frame. I've now got about 80K miles on my rebuild I did on my own with no leaks or troubles since I bolted it back in. I used a Precision Industries Converter sourced it through Probuilt Automatics which is also where I ended up buying all my parts. I started with one of their kits and swapped and upgraded parts till I had what I wanted. The guy that runs ProBuilt was an excellent source of knowledge about which upgrades are good to do and which are just flagrant; like where it's good to add an extra clutch plates and which valve body and pump upgrades can be used together and which can't. Mine also had to have several hard parts replaced due to wear/broken that were sourced through a national used parts supplier (pump input shaft support, excessive wear on a non-hardened sunshell, excessive snap ring wear on center support). I think I ended up saving about 1/2-1/3 the cost of what BTS was going to get from me at the time (2014). I did later stop by BTS and have them work over my valve body and that was worth it. The truck has shifted more consistently and smoothly since that was done.
