Search on Tim King here, you'll find his trans thread with contact info.
I have a TEP valve body/channel plate with the modded spacer plate. There would never be a regret buying another. From what I've heard about the 4340, I'd stick with a stock input shaft or the 300m/Intense turbine shaft. I've heard of a bunch of 4340 failures, they don't hold up to ZZP's claims.
Agreed on many trans shops rebuilding to stock specs. Thing there is our clutch packs have a lot of play in them with just a stock build. Thicker steels, additional clutches etc etc should be used to clearance the packs. That way you don't have the slop and additional wear during engagement.
You want someone that works with the 65 and understands it's various issues etc. Similar to you being on this forum for 3800 info.. you want a person that knows the 4T65 platform.
