I believe that at one time they had a cap that fit where the road tube went into the block . It had a 1/2 hose fotting that went to a inline pcv valve that went into rear of carb.The ones i remember were on mid 60's corvettes. may try zip products or ecklers if they are still around. the other one put a plug in the road pipe hole at the back of the motor ( i think a freeze plug ) and change the filler pipe on the front of the manifold to a sealed cap with a fitting on the sside for a pcv valve. i liked that with a set of the old aluminum vette valve covers.
