Longbox55, I worked in the Chevrolet Assembly Plant at Van Nuys, Ca. in '57 and '58 model years. All our 1957 engines were 283's, no cars assembled at Van Nuys had 265's. As for the cams you could grind a slot in the rear journal and use the later cams in 265's, I have done it several times, the lifters oiled properly with this modification. I made a 283 out of a 265 by boring it .125 oversize with no problems, ran 8000 RPM plus lots of times at the drag races. The 265 blocks were quite thick in the cylinder walls so a big overbore was no problem. You can also bore a 283 oversize .125 and that makes a 302. The later blocks, i.e. 327, 350, and 400 won't take that much overbore.
