I ran the the 516's on a low compression 383 in a 3400 lb B-body. Low 13's at 105-106 mph. They had the 1.74 exh. valve (284/484 cam, 750 AFB, TM-6). My 60' was poor (1.99) due to chassis issues.

The 516's with the 1.74 exh. valve will flow well for a street/strip motor that won't be spun past 6k rpm's. Just my opinion, but the better quench, compression and intake manifold fitment outweighs the whatever advantage a 906 may or may not have.

Besides, any flow above .500 lift would never be realized with a 484 or 509 cam. And with a B-body a high velocity port that is more efficient will serve you better than a high flow port that won't see it's ultimate usage anyways. Heavy cars with only a 3k converter and street/strip gearing don't need huge ports.

The short side radius of the ports are where those heads need the best attention for flow. Intake port gasket matching and bowl work also are inexpensive if you do it and big gains are in there. I gained 3 mph through the traps with a 3" exhaust system added at the same time.