LA360 initial timing too high - are there different timing covers?

Good info. I looked it up too and the durations are 276/288. LSA looks like 114 with a 109 ICL 'as ground'. Not terribly radical buut.

To be able to compute out to the cranking compression you found, with your cam:
- was installed wih little or no advance (That's not the same as putting the key at 0 degrees.)
- the head gaskets are Felpro 5883PT's
- the pistons are deeper dished or lower compression height truck pistons

With the cam out, it would be easy to put in another one, like a 260 or 256ish range with the same lift. (Crane, Lunati Voodoo or Comp XE/HE. Is that your thought?

Do you feel like pulling heads and looking things over and putting back in some thinner head gaskets? (Mr Gasket 1121G) I know I would want to put some sort of bore gage on a few bores to see if there is taper or out-of-roundness, and see how far the top edge of the pistons are from the deck and the dimensions of the piston top's dish.