cam selection

There is some wrong/bad info here. A slant six engine that came with a solid lifter cam, can be converted to hydraulic, vice/versa. There is no difference in the blocks. The difference is the cam, lifters, pushrods, rocker arms, and cam bearings. These must all be used a "package".
I agree about Clifford being not the best company to deal with, but their 1.6 rockers, are not the stock stamped pieces. They are cast items, like the old "gotha" rockers, from the 1960's. There is a picture of them over atslantsix.org. The Clifford 1.6 rockers will only work with a solid lifter cam, not the hydraulic.