My combination is a 383 block, bored .030 with a Muscle Motors 489 stroker kit. I have studs and a girdle in the bottom end, we are using a Bullet hydraulic roller cam with 573 lift, and 242, 247 duration @ .050, and a 110 LSA. 440 Source Stealth heads, Crane adjustable rockers in a 1.5 ratio, and a Mopar M1 with a Holley 750DP. This is all going in a 4200lb car with a Turbo Action 3500 stall converter and manual valve body. I have 4.30 locked 8 3/4 with 29.5" tires. My goal is 600hp and a 12 sec time slip, is it possible with this combo? I had issues the first time this motor went together, and now we are on to round 2, and my problem is that the engine builder has noticed that the rocker arm position in relation to the head of the valves is not constant, and it is actually off by quite a bit(almost on the edge of the valve). I don't know if I just by a quality set of roller rockers if this will solve the problem. So what I am asking is will good rockers solve this issue, or should I buy better aluminum heads, and if so, which ones? It almost seams like a casting defect to me in regards to the heads I have, what does everyone think? I am also torn between the Eddy performer rpm heads, or a set of Indy EZ's. Any and all suggestions and opinions will be grately appreciated.