Standard AMC heads with press in studs will have to modified to screw in studs; and guide plates are required when running any roller rocker. If you have gone to the level of needing roller rockers you most likely have already made these modifications to your heads anyway... Most rockers are available for 3/8 and 7/16 studs so if you have to have your heads modified I strongly suggest going with the 7/16 while you are having the heads machined. If you are having new studs put in to your heads ask the machinist installing them to dress the tops flat - the locking nuts will engage the studs better and you'll have less of a problem with your nuts backing off over time.

Now for ratios, these rockers are available in 1.6 and 1.7 to one. If you opt for the higher ratio arms be absolutely sure that you have adequate valve to piston clearance or really, really, really bad things will happen. The last thing you want is a piston smacking and bending a valve when you turn the engine over. Most lower compression engines will have no problems but if you have changed pistons you may need to change pistons again or have new fly cuts machined.

Installation and adjustment - Consult your manual for valve lash specifications but for most hydraulic lifters, zero lash and 1/2 to 3/4 turn of the retaining nut is usually correct. I prefer to run my lash settings on the loose side. Mechanical lifters usually have a setting of .01 ~ .014 (but I have seen them up to .03) and remember to set them hot. Don't forget to add or subtract the correct amount if you have changed the heads to aluminum.

Testing - Since I don't have a dyno I can't tell you if horsepower changes but just the piece of mind I now have using a high quality arm is enough for me. After months of running these arms I have never needed to make an adjustment and there seems to be no fatiguing of the aluminum.