Pull the carb and intake off and see if the intake ports have oil in them
If so add thicker fiber type intake gaskets
If I was you while you have the intake off I would remove the intake valley pan, intake gasket, and then sit the intake manifold back on the heads and use a feeler gauge to check the clearances between the intake manifold and heads, top and bottom on all four corners If it has a lot of variances have the intake head surface milled to flatten it
I've had to do that more than once on aftermarket new and used aluminum intakes
I've also had to stack intake gaskets (.060 to .120 thick) to seal the intake to the heads It worked well and the motor like it