[JLMounce]

On a street car I would go with D ports simply because of manifold/header availability. The Kauffman and Edelbrock D ports have slightly less CSA which should help low speed torque production on the street over the larger ports in the round port heads.

Honestly though I don't think you can really go wrong with either.

If you're going to stick with your 5C heads right now, I think staying with a flat tappet setup will be fine. What I would do however is while you're having the heads put together, elongate the pushrod holes to accept a 1.6 to 1.65 ratio rocker. Not only will that rocker add valve lift, but the valve action increases, which increases the area under the curve of the tappet, in essence doing the same trick that roller cams get away with.

On the crower 60919 going with a 1.65:1 rocker nets you .517" of lift compared to .470 with a standard 1.5:1 rocker. A head with some light clean up and bowl work should like that bit of added lift.

I'd stick with the Performer RPM, or a stock intake.