Is the OP “SURE” the cam card he posted is the cam that’s actually in the motor?
If so, the 924 springs aren’t at all suitable…….but I also agree the cam is a big mismatch for the combo.
Step one should be have the heads set up properly for whatever actual cam is in the motor.
IMO, the talk about going to 906 heads is pointless.
It’s easier to correct the problems with the current heads then start in with a new can of worms reworking some 50+ year old factory stuff.