I dont think there are any 620 parts that can really benefit you on a 60. 620 block is shorter, so the pistons will also be shorter. Im thinking, dont know 100%, that the headbolt pattern is also different. Sparkplugs are in the side of the head on a 620/630 instead of in the block like the 60. Airplane pistons are really short, and work well for a stroker application 5.750" bore Pratt & Whittney is 2.605" compression height 6.125" bore Curtis Wright is 2.705" compression height 620 cam is the same as what is already in the 60. It looks different because it has a distrubutor gear on it, but the lobe profile is the same. Now then.... 60LP pistons will give a boost in compression. The cylinder head will benefit from a performance valve job and releaving the "eyebrow" as far from the valve as you dare w/o hitting water. Bigger valves become more shrouded as they come closer toward the eyebrow and the cylinder wall. It wont hurt to take a diegrinder w/ a sandpaper cone and smooth out the casting buggers in the runners. Roller rocker arms are worth a few horsepower as well.
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