Well,there are actually lots of differences between the early and late style engines,but i'll condense it here.....AMGeneral....can you explain how to identify early and late and the advantages of either?
The earliest engines(FSN 2815-980-7092) Had 9/16 cylinder head studs,5 ring pistons,and had metal bearings in the injection pump governer.
FSN 2815-087-2273 engines had 4 ring pistons,5/8 inch head studs,and had bushings in the injection pump governer made of Teflon.
FSN 2815-045-6865 engines had all the improvements listed above,plus improved cylinder heads and crankshaft main bearings
To add to all the above confusion,the early engines also used a large Schwitzer 4D-554 turbo and 1 5/8 inch piston pins.
The later style used a Air Research 40790-1 turbo and had 1 7/8 piston pins.
I have seen power ratings from 205 hp to 220 hp and 611 to 720 ft/lbs torque,depending on early or late engines.