I have decided on the camshaft to be tried first in this engine-A Comp High Energy 268 single pattern. I like to machine the spring seats to accommodate a 1.25" Chev style spring. I modified an everyday tool to machine the guideboss/spring seat on Mag heads. These Manley springs are inexpensive and my goto choice on mild builds such as this. They fit nice and snug and are completely compatible with the stock Mag retainers. Installed height is currently 1.68"J.Rob