68 truck 318 cam. How big can i go?

68 d100 318 np435 4 speed with like a 7:1 granny, 3.73, 29" tires, manual brakes/steering. I understand compression is about/under 8:1. Ported/polished 302's with big valves, rpm intake or a single plane, 600-750 eddy card (I want to try a Holley, but I have the eddys). Headers to 3" duals, h-pipe, dumped in front of the axle.
I want the biggest cam I can run for an rpm limit of 6500-7k. Not much strip time, but I drive 95% of the time at 65-75 highway, but I like to tear around. No towing. I'd like to see 450hp, and a power and of 4000-7000. I've read IQ52'S posts on low compression builds, so the compression doesn't bother me. I may throw a turbo on it in the future, and am also wondering if the cam should be changed at that time. I'm guessing something in the 275-285 range with high 500's lift. I've no experience with big cams and small blocks regarding driveability.