As long as the engine can breathe you're fine. Chevy did not start using a PCV system until 66in CA, 68 in the other 49 states. All small journal small blocks have the boss on the back for the road draft tube, but the last year it was used was 63. 64 and 65 CA, 66 and 67 49 state cars used a tube in the front of the intake with a vented cap. 66 and 67 in CA used the same setup with a hose from the tube to the carb. I ran a similar setup on a 350 with an early intake and Corvette valve covers years ago with no problems.
Devin
