M33P

Which of these would you recommend for a street only 408 with cathedral heads? Planning on tfs 225s. 11:1 compression going in a cruiser 64 cutlass will never see the track.

68Formula

Which transmission (and gearing if it's manual)? Torque convertor stall? Rear gears? Shorties or long tube headers and which size? Intake manifold type? Throttle body size? What fuel and octane?

Honestly, even the SUM-8729R1 is probably too big. Maybe with more compression or 427+ cubes. The DCR is only 8.1 with your setup.

This would drive better with an earlier IVC and have the same aggressive idle:
https://www.summitracing.com/parts/sum-8711r1
Stage 4 Pro LS Cam, Extra Clearance 234/248 113.5 +3.5 .625/.605 Lift

At most maybe this one with a decent stall (or wide ratio manual) and 3.73+ rear:
https://www.summitracing.com/parts/sum-8709r1
Stage 4 Pro LS Cam 238/246 113+3, .625/.605

Summitracing

@68Formula brought up great points about extra info needed before making a recommendation. To add to that what does the exhaust system consist of after the headers? Let us know this info along with the info from 68Formula and we can come up with a recommendation.