i need help w/duster engine

Well now that we have a little more information we can make a better determination. The problem I see is that getting a spring heavy enough for the roller will not allow that kind of lift with a standard length valve. This is the reason the long valve W2 was developed. All the later performance heads from Mopar have long valves for the 2" installed height valve spring as well. There are things you can do like special retainers to get close to that 2" height but I don't know if that will be enough. You still need .060 left before coil bind at max valve lift.

You will also still need to do the aformentioned block modifications to the lifter galleys so the engine will have to come out and apart anyway. Once you get the head situation correct and the block mods done you can do a mock up assembly of the #1 cylinder and measure your valve to piston clearance, or lack there of. I don't know of any other way to calculate the clearance you'll have even if you had every measurement needed, which you don't, other than an actual mechanical check. You will need to measure through a sweep of typically 10 to 25 degrees BTDC on the exhaust lobe and 10 to 25 degrees ATDC on the intake side. Measuring the cam you have now is futile and doesn't really tell you anything about how much clearance the new roller will have because the rate of lift, duration, open and closing timing events on the roller cam are going to be radically different.