273 mild build-----

If it's the late style 273 then I would use a performer 318/360 intake as the ports are smaller like the 318 has and will be close enough to not worry about mismatch. For a cam I would use the summit K6901 which has .441 lift on both and 218/228 @ .050 duration, this is just a bit larger than the 318 came with and smaller than the 340. I guess it would be more like a 360 2bbl cam, slight lope and lots of low end TQ. I would top it off with a 670 street avenger, and good manifolds and or shorty hedders, which ever you choose.

This would make a nice street combo. For the heads I would do a 75* bowl cut on both the intake and exh. sides and a good VJ and leave the rest alone. The bowl cut will help low lift air speed. Also I would backcut the valves on both and you should be good to go. The backcut and the bowl cut should help the air flow about 15% with nothing else being done. To me this is the best and cheapest bang for the buck.