Well if it is indeed a 59 GMC engine, it would be bored .040 over. The 59 Pontiac motor, and the 59 GMC motor had 3 inch main bearings. The 347 and the 370, as well as the first series of 336 motors used smaller main bearings.
Why am I rambling about the bearing size? You can get a stroker crankshaft for the 59 and on Pontiac motors to increase the stroke by 1/2 inch. I have a 59 pontiac 389 in my 59 gmc that has been bored .030 over (4.0925)and stroked to come up with 447 inches.
