Is it difficult to locate the head ID numbers while the engine is still in the car?

Impossible to see in the car if the muffler hanger is on the pass side and the heater outlet is on the driver side.

best wishes, Steve
Rear Engine Spec. Inc. Golden, Colo.

1962 spyder 3.0L turbo---1965 Crown V8
1967 monza 110/4---1968 monza 110/4
1971 amante gt 110/4
CORSA/RMC/PPCC/V8 Registry

You can remove the corner shroud bolts to pry and peer with a light. Sort of a pain and difficult to pry enough but can be done if you're determined.
The exhaust manifold limits travel on the left.
The coil, side shroud, corner shroud and exhaust hanger limit travel on the right.
It helps to have the possible numbers on hand in case you can't read all the numbers but can maybe confirm a hypothesis.
It's more difficult if it's grungy in there.
I had a guy with a EM head on one side and a LM head on the other side. I tried to talk to him about vastly different compression ratios but he quoted same volume specifications in the Tech Guide. It was the first time I started questioning some of those specifications but haven't gotten around to doing a study. I don't know whatever became of him and his Corvair.

Jim Brandberg
Isanti, MN
CorvairRepair.com

Thank you for your information, gentlemen.

The numbers can be hard to read when the head is clean and off the car.

Joel
Northlake, TX
5 Ultravans, 145 Corvairs and counting...