I would not think to open up the ports to gasket match them. They look too big already, might be low on port velocity? Hard to say, by just looking @ the pics.
Maybe if you had a measurements of the intake ports & exhaust ports I would have a better idea on just what size those ports are. Valve sizes in, ex? I forgot.
I would definitely not lower the floors of the ports. You would want to leave those floors alone, unless there is a big mismatch between the intake manifold & the head.
On the 1 BBL intake , are the ports divided? It's been so long since I have the seen the 1 BBL & 4 BBL Pontiac Sprint 6 intakes side by side I cannot remember how they looked. Got some pics?
Did the 4BBL Sprint 6 have better con rods than the base line 1BBl Pontiac 6? I heard they did but never confirmed it.