That's the 305 Magnum. Comp Cams says: Pro Street/Bracket, limited street driving, 3,500+ stall, racy idle, 10.5:1 CR. If you run less than 3,500 stall, you've got problems. Also, your compression ration is likely too high for pump gas.

I wouldn't judge these heads strictly on the intake port volume. This is the head that GMPP puts on the ZZ-4 block to produce the "Fast Burn 385" motor, and that the dealers like Sallee Chevrolet use on their "ZZ-383." In both of those engines, they get about 9.7:1 compression with a flat-top piston. (I'm not saying that these are the same flat top piston in 67's engine.) All I'm saying is that with the right piston and cam, these heads work really well on a SBC.

With all that said, it's still too much cam and too much compression for the street. Eric's recommendation for about 15 degrees less duration on both sides is in the ballpark, and makes the cam very similar to Chevy's LT4 "Hot Cam." Get the compression down to about 10:1 and use about 2400 stall. Seriously, you will not like that cam on the street. I like the heads, though.