Do I need adjustable Rockers with Hughes 318 whiplash cam?

I have a 70 318 block at the machine shop now with #675 small valve heads, the are just freshening up the block and heads, new bearings are being installed. I told the engine builder I have the Hughes 318 Whiplash camshaft and showed him the specs. He said that for my setup I will have to switch over from the 318 fixed rockers to a set of adjustable rockers or adjustable push rods, because the lift on the exhaust is over .500".

Is this true? Do I need to get different rockers and pushrods? Hughes Specs say the lobe lift for 1.5ratio rockers is .480" Intake and .516" Exhaust.