Here's what I have guys.

The first and/or second digits indicate piston displacement They could be 6,8,9,10,11,12,13(what we use),14,16,17,19,20,22,23,24,25,26,28,29,30,32, 35,40 or 42 cubic inches.

The third digit indicates basic design series, it could be 0,1,2,3,4,5,6,7,8 or 9. I'm not clear on this yet but it has something to do with aluminum bore,steel bore , comercial, industrial etc.I'll find out more and let you know.

The fourth digit indicates crankshaft position, carb. type and governor type.
0-not used
1-horizontal Vacu-jet
2-horizontal Pulsa-jet
3-horizontal Flo-jet
Pneumatic Governor
4-horizontal Flo-jet
Mechanical Governor
5-vertical Vacu-jet
6-not used
7-vertical Flo-jet
8-not used
9-vertical Pulsa-jet

The fifth digit indicates type of bearings, reduction gears & auxilary drives
0-plain bearing(bushing)
1-flange mount plain bearing
2-replaceable ball bearing
3-flange mount ball bearing
4-pressure lube
5-gear reduction
6-gear reduction rev. rotation
7-pressure lube
8-aux.drive prep. to crank
9-aux.drive par to crank

The sixth digit indicates type of starter
0-without starter
1-rope
2-rewind
3-110 volt electric
4-12 volt starter/generator
5-12 volt starter
6-altenator(6-formerly wind-up start on 60000,80000 & 92000 series)
7-12 volt starter & altenator
8-vertical pull rewind