I've been seeing a few basket case engine or bare cases type of deals going on ebay here for a while, and better than half of them insist that they don't know the year or model...  As far as the 70' to 80' models go, the engine numbers are located on the right front of the right side engine case... These are usually stamped on a flat "plate" at the apex of the cases where the cylinders meet...

THE MODEL CODE PART:

1A :  FL, FLP, FLPF--- 74 cu. in. (1200 c.c.)

2A:  FLH, FLHP---  74 cu. in.

3A:  XLH--- 55 cu. in. (900 c.c) thru 1971, 61 c.u. in. (1000 c.c.) from 1972 on...)

4A:  XLCH---  SAME AS "3A"

3G:  FLH---  80 & 79 Classic

3H:  1980 Classic

4E:  XLS

5H:  FLHS 80

5A:  GE--- Electric Start Servicar (trike)

2C:  FX---Kick Start Super Glide

9D:  FXE--- Electric Start Super Glide

7F:  XLCR--- Factory Cafe Racer

6H:  FL 80

9H:  FLH 80

2H:  CLE--- (Sidecar)

7H:  FLH--- 1200 Police

8H:  FLH--- Shrine

1K:  FLH --- 80 Shrine

The sequential production number will have five digits, and the model run starts at 10,000. The numbers start at 60,000 after 1/1/78, and the CLE they start at 80,000.

For the year part, the last two numbers in the sequence help you out there...  'H' stands for the bike that made Milwaukee famous, except in 1980; the letter changes to 'J', maybe because corporate types don't have to pee in bottles to keep their jobs... And the number immediately following is the year....

EXAMPLE: 4A13801H6  would be the 3,801st 1976 xlch sportster to roll off the line....

Now, I got this information (more or less) from a book called "What Fits What On Harley-Davidson Motorcycles"  by Mike Arman and Kurt Heinrichs.... IT IS NOT A HARLEY DAVIDSON PUBLICATION, BUT IT IS ESSENTIAL REFRENCE MATERIAL FOR ANY WOULD BE BUILDER OR WRENCH.... It's not a large book, (only 80 pages) but it is written in such a way that yer average ordinary human being can read and understand it... Plus, it takes a look at a wide variety of parts interchangability on the American V-Twin with more than a bit of humor that is worth the purchase price anyday....  I MAKE SURE THAT I SAY THIS BECAUSE THIS IS, IN FACT, COPYRITED MATERIAL, AND I WOULD FEEL LIKE CRAP IF YOU DIDN'T IMMEDIATELY RUSH OUT AND BUY 10 COPYS OF THIS BOOK TO SHOW YOUR APPRECIATION TO THE INDIVIDUALS THAT PUT IT ALL IN EASY TO ACCESS FORM FOR ALL OF US SCOOTER-TRASH TYPES OUT THERE... Not to mention, the part i put on here for your information has been sufficently modified and is commonly available enough that copyright probably don't apply... Oh, and i bought the book....

Be Safe Ya'll....