Go to a machine shop and see if you can have the crank cut, and then buy oversized bearings to match how much the crank had to be cut. I think this would be the cheapest way to fix your problem. I personally would buy a 383 stroker kit, but the above mentioned way should work just fine. Also go to your local parts store and buy a Haynes engine overhaul manual for your motor, it will be the best $19.99 you have ever spent on your motor.