My 283 is 60 over with flat tops. the heads are off a mid 80's 305 which I get off ebay rebuilt for $250. I took all the valves out, gasket matched them and did alittle short side radius and port work, nothing special, and put them back together. I had a summit 1103 cam in it, and man did it sound mean!! only problem was the th350 trans (I know I should have went with a manual but pedal room is an issue) did not like the cam, nor did the fuel injection, and the crap 2.75 rear gears probibly would not have liked it either.
I ended up putting a summit 1100 cam in it now. The engine idles quite nice and it will actually run in gear now!! Engine seems to run great with the new cam, probibly not as much top end now, but that ok. Still spins the tires on dry concrete (of coarse the car does not weigh anything)
I like the little engine, and if I can get a good tune on it I hope for 20+ mpg.