th350 to 700r4 to np205 question

[man-a-fre]

I have a 72 blazer with a th350 np205 combo that im wanting to put a 700r4 in front of the np 205 i know advanced adapters sells an output shaft for the 700 to go to the np205 then i move the engine forward,my question is will the rear output out of the stock th350 or any other stock trans be the right part i need so i dont have to spend the 200 bucks for the shaft. Ther has to be a stock shaft that is the same as the advanced adapters i would think.