Do I need adjustable Rockers with Hughes 318 whiplash cam?

Two comments....
1. Given the Mopar small block pushrod angles, there will be slightly less than .500 lift. Although lift has nothing really to do with rocker choice until you get a bit bigger.
2. Best bet would be to contact Hughes. Their cams like a decent spring, and may use an anti-pump-up lifter for it that require adjustablility in the rockers.