426 rocker arm ratio

301's are the same, at 1.5:1 I think. I put Murphy's roller Rockers on last year that are 1.75:1, which got me around .075" more lift. But, better pay close attention to piston to valve clearance with stock pistons. Mine had deep enough reliefs. 

I think they are .200" deep. But, I also have a grouind cam, and a stroked crank. Stroking the crank increases compression ratio. When I assembled mine, I calculated(computer program in old laptop)comp ratio, and even with the stroked crank, the reliefs dropped the comp a full point from 15.5 to 14.5 if I remember right. So unless you're stroking the crank, I wouldn't cut them any deeper than needed, or you'll lose the lugging with too low a comp ratio. 

200-7000-7010-7020 engines were always 15 to 1 compression (book info was in error)and have the same cc's in the bowl of a 180-190-190XT's do and they are 16 to 1. The difference is the 15 to 1's have .030" diameter (.015" meat) removed above the top ring to keep the piston head from swelling and dragging on the sleeve. The early 6060-6080's were truly 14 to 1 and their bowl cc's were more. Later on they were 15 to 1 to improve starting and when overhauled were probably 15 to 1.

well, mine I cheated, and bought all the stuff used. lol! Now when we built Matt's a couple years ago, I had my machinist buddy shorten the top of the piston down the .250" in his cnc lathe. The bottom of the bowl as well. I had him pretty much maintain the original shape, except we kept the top of the bowl slightly rounded, instead of the sharp edge. He then cut the valve reliefs in his cnc mill.