Haibach,

I think it will be fine, I have run a nitrous fed cast crank stock rod 440 in a 63 Plymouth to a best of 9.69 135 , that was 15 years ago, I belted piss out of it and the engine still lives. It has been semi retired now running NA 11.00 in my sons Aussie Valiant street strip car, all good.

5 lbs go for it !!!!

Cheers