Hi Bob! I'm still around.
Info for GAS engines (not LP, etc.):
WD45's had 6.5:1 compression ratio engines and as said had a 45-xxxxxx serial number. Oil filter was a bypass system. Rated engine speed was 1400 rpms.
All D17's had 7.25:1 compression engines and serial numbers 17-xxxxx and a -M suffix code. Early Gleaner E engines had the same 7.25:1 CR and the -M suffix. Tractor engines were rated for 1650 rpms and combines for 1600. Early D17 engines were bypass oil filter. Full flow oil system came on at tractor SN 24001 for the D17's and this was before Gleaner E combines were made so all Gleaner engines had full flow oil systems. Also the D17 crank was different with a center thrust bearing and larger mains if I remember right.
Later years Gleaner E, EIII (1968 only) combines and 170 tractors had 8:1 CR engines and had a -Z suffix code in the serial number. Rated engine speed for the tractor was upped to 1800 rpms.
175 gas tractors had a 8.2:1CR engine and a -V suffix code. Same 1800 rpms. 175 gas tractors got a larger carb intake.