OT, getting a free "1977 Olds V-8", what is it?

Your right, it was era specific. Prior to 77 the displacements were not cast into the blocks. From 77 on, the blocks were cast using different cores and have windowed main webs.

 

It probably had 2.41:1 gears in it too. All the headers and cams in the world won't fix that.

 

Anything after '76 were junk blocks...

 

I used to drag race a 1969 W-31 325hp 350cu in Cutlass. With headers, slicks, and gears it ran 12.67 at 107.98 at a 1500 foot alt track. Cast iron intake and Quadrajet.

Built a mini-rod pulling tractor with a 403. Put ported 350 heads and a W-30 camshaft. The 350 heads were smaller chamber and raised the compression. I didn't run a tach at first, put a tach on and found out I was over 7000 rpm during a pass. It was beating 406 roller cam al. head Chevys.

There are a few,apx 500, 403s with a big X on the side. These are high nickel content blocks.