Stock rockers "can" work. I feel that the roller cams NEEDS a roller rocker system. With .516" lift, you will have retainer to guide issues on the exhaust side, though. If you trim the exhaust guide for cleraance, you will need to install a good seal (i.e. PC seal) BUT they will NOT work on a stock exhaust valve. PERIOD!!! With stock heads, the roller cam is just barely doable. I don't like that much lift with stock stuff. It works for some people, but I am concerned about retainer to guide clearance. Trimming the rocker pedistal is pretty easy off the car. On the car, it can be done, but it is "iffy" You need to grind the side of the pedistal to gain clearance on any of the roller rocker out there. When I port a set of heads, I always do this mod. I never know if they are going to use rollers in the future or not. It only takes about 10minutes when they are on the "bench". Do a search on this topic and there are lots of pics already posted.