What #s are there and where are they located on the heads. I'm pretty sure these are from late 60's but not sure. How many rect ports did GM actually make?

Kevin
The casting numbers are under the valve cover on the head with raised numbers. They are easy to see. For cast iron heads the #s are in 65(3856208) 66(3873858) 67(3904391) 68,69(3919840) and 70 was 3964291.

RECTANGULAR PORT - Valve size 2.19 intake, 1.88 exhaust
Casting Years CID Chamber CC HP/RPO/Comments
3904392 1967 427 Closed 106.8 430, 435 L-88/L-89, 1.72 ex
3919842 1968-69 396 375 L-89
427 Closed 106.8 430, 435 L-88/L-89, 1.84 ex
3946074 1969-71 396,402 375 L-89, 427 430 L-88/ZL-1
454 Open 118.0 425, 465 LS-6/LS-7, round ex
10051128 1990-94 454 Semi Open 400cc, bowtie, sym port
14011077 1989-94 454 Open 118.0cc, 295cc, replacement, C port
14044861 1989-94 454 Open 105.0cc, 380cc, bowtie, W port
3856208 1965 396 Closed 108.9 375, 425 Z-16/L-37, 1.72 ex
3873858 1966-67 396 375 L-78
427 Closed 108.9 425 L-72, 1.72 ex
3904391 1965-67 396 375 L-78
427 Closed 106.8 425, 435 L-71/L-72, 1.72 ex
3919840 1967-69 396 375 L-78, 1.72.ex
427 Closed 109.0 425, 435 L-71/L-72, 425 COPO
3964291 1969-70 396/402 375 L-78, Intake Port 325cc
427 425, 435 L-71/L-72
454 Closed 450 LS-6, 108.0cc
3964292 1970 454 Closed 450 LS-6, 109.0cc
3994025 1971 454 Open 425 LS-6, 118.0cc
3994026 1971 454 Closed 425 LS-6, 118.0cc
6258723 1971 454 Open 425
6272990 1971-94 454 Open 425, 118.0cc, 325cc
14096188 1987-94 454 Open 118.0cc, 325cc, replacement
14097088 1989-94 502 Open GEN V, 118.0cc, 325cc, replacement

wow Thanks Guy's that's awesome.

well, I was way off. The # to the left says H O 81. And the right side says 6272990. So with what info you gave me these are 1981 990 heads, correct?

Yes, probably OTC or crate engine heads. They were used on both the crate LS-6 and LS-7 engines.

So does that mean these are supposed to be 325cc intake runners. My engine man says that wrong. He thought they were around 280 to 300cc runners. Are there different versions of the 990's?