have heard mixed reviews on the scorpion rockers, but that was a few years ago so maybe they improved them. sttandard ratio is 1.5 but some go to 1.65 for added lift/duuration, but you need to be sure the heads pushrod hooles are clearanced for 1.65's. they sell a pushrod length checker to measure the length pushrod you need. if you are doing it yourself thats the easiest way to verify that.
most all rollers will fit under stock valve covers, but you may need a thicker gasket or spacer. felpro sells an extra thick gasket that works good for roller rockers. i have harland sharp rockers & locks under stock valve covers & they fit fine.