There's red flags popping up all over this deal in my opinion. Like others have mentioned, look into a transmission from a builder like Abruzzi or Carl Rossler. I'd hate to see you spend $ 2600 for that trans. and find out it's junk inside. Since you have posted this asking if you're doing the right thing, it sounds like you have doubts also. Follow your instincts. You'll probably get some flack from the owner, but you'll still have your money.