Fixxxer22
As said, by Eddie and Bob, always check the lifter bore clearance not only for clearance, but also for being out of round. The Morel, lifter is what I use on every build. The problem with any lifter is the clearance and any side loading of the lifter, caused by the bore not being true to the cam lobe. This can be corrected by indexing the lifter bores installing bronze sleves. Morels require a max clearance of .0015 and a min of .001. I use a BHJ lifter true set-up in my milling machine. the bores are drilled and reamed to about 1.000" then we install bronze bushings, drill the oil galley holes through the bushings, then ream the bushings, the block is then put into a honing tank and the bushings are finish honed to size.
Your lifter to bore clearance should be .0015 for a marine application. I have found that for example: New Dart block clearance is .001-.0012", on a World block .002-.0022", GM Gen5,6,.002" anything that has alot of time on it
.0025-.0028". One of the problems with a World block is the lifter bores are short, plus they have a under-cut- radius at the top of the bores. Any of the older Gen IV blocks do not have the taller lifter bores and are most likely worn and out of round. I have in the past extended the bronze bushing out of the bore on the top to give more surface area to the lifter.
Have you machine shop, check every one of those bores for clearance with a bore gauge against the Morel lifter O.D. size. If they say only 1 or 2 are worn, you are better in the long run doing all 16. The cost should be 450-500$.