Buffalo Engineering sells a 700R4 flex plate that has been modified to fit the stovebolt crankshaft by welding a new center into the plate with the proper bolt pattern and re-balancing it. It's probably worth the cost to buy that one. It's got the correct starter ring gear to work with the stovebolt engine, also.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!