Side by side photo of the 842 vs 074 head?

[big gear head]

I may be wrong, but the L89 head is closed chamber and the '69 L88 head is open chamber. There is a huge difference in the shape of the chamber. Also, I believe the L89 head has square exhaust ports and the '69 L88 head has round exhaust ports.

[RALLY]

big gear head is right. I owned both heads at one time. 074 head like he stated was an open chamber head, which is better for flow, and round exhaust ports. Valve stud cast area was prone to cracking, but i used as long as a valve stud i could for better support in that area. 842 was a nice head, but as stated closed chamber with square exhaust ports. You are right by looking at these two with valves covers on and exhaust manifolds or headers, its hard to tell until they are off the motor. BB Chevy heads were notorious for bad exhaust port flow. I had my 074 head exhaust ports opened up under the valve.