Scott McClay told me recently that he only sells parts to customers who purchase his transmission. I was attempting to purchase his side case brace and deep pan. I have experienced several cracked cases in the bellhousing area about where the recess is formed for the dipstick and the case is thin. I fabricated my own case brace from aluminum plate and purchased a very nice cast aluminum deep pan from Turbo Action. These changes hopefully will strengthen the case enough to prevent further cracking, so far no further problems. I don't think you can easily use a TH-350 converter with a simple shaft change, but require a more involved internal modification.
There is an excellent Canadian TH-200 builder, Jim Mantle, located in Black Creek, B.C. He does his own proprietary valve body and extensive internal detailing, and at an affordable cost. I've run Jim's stuff for years with excellent results, and he's a great guy to deal with. Jim races in stock eliminator himself and understands what we need. Send me a PM or email me at
grant4060@yahoo.com if you are interested in contacting Jim and I'll get back to you with his contact info.