Your headers will be perfectly fine for your intended usage. I have the same ones on my 408 and made 543 hp and 562 torque with hydraulic roller from Hughes 237-241 @ 0.050, lift at .580. I also wanted a driver. Although I have had no issue with my hydraulic roller which WAS a custom grind through Hughes, I may switch to a solid flat tappet. Engine revs so quick, my personal safety RPM is 6000 to be cautious with the hydraulic roller lifters, with solid flat that fear goes away. Personally I'd never use a solid roller on street unless it had a bushed roller wheel. My friend had one come apart in a well built small block Chevy, it destroyed the engine.
