There's a way to modify stovebolt engines to run main bearings for a big block Chevy V8, but it involves some pretty sophisticated machine work, and welding up the first two main bearing journals of the crankshaft. It's definitely not part of a backyard rebuilding job.
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!