the pic(340sFastback)helped me most about a month ago. if your roller tip is outboard (exhaust side) then you would need to raise the valve or lower the shaft.
i have a bag of shims from mancini if you need'em
I agree. I went through this with a set of Harland Sharps when I put my 340 together. I ended up shimming the stands and ditching the HS rockers as they were really designed for longer valve stems. I ended up with MP iron rockers (which were junk, BTW). Those had the correct geometry, but had .010" clearance on the shaft. I sent them out to have them bushed and they're OK now. I should have stuck with stamped rockers.