It ain't gonna happen tonight - finding more numbers, it's pretty late here. The real question is if this motor can have hydralic lifters. What do hydralic lifters feel like? What can cause this springy resistance in the rockers even when the valves are closed?
On my 216 the inactive rockers had free play.
Can some distant PO have rebuilt the engine - whatever it was - with hydralic lifters?

It may not be the easy way, but it is the Cowboy Way - Ranger Doug
Beware of the stories you read or tell; subtly, at night, beneath the waters of consciousness, they are altering your world. - Ben Okri
1953 Chevy 3100
1960 Volvo PV 544
1941 Chevrolet Special Deluxe