Chad,
Here's a good example to practice your Sportster-spotting skills on: http://baltimore.craigslist.org/mcy/4823059334.html
1961 XLCH - Good-looking, good running, clean title. Except that it's about 8% original, not 80%
Look at Craigslist Photo #2, then look at Dave Carlton's 1961, 1967, and 1969 in the Gallery section. See if you can match the Craigslist parts to parts on Dave's bikes. You won't find some of them, as they're even later model. I picked out just a few of the AMCA categories...
Frame / Fork
-- note the lower triple tree cover - what years?
-- rear shock absorbers - what years?
Front Fender
-- yeah, it's partially cut off, but look at how it mounts
Handlebar / Grips / Controls / Comp Release
-- ???
Headlight / Magneto
-- headlight - look at the two-hump ring holding the lens on. This one's half-chrome, half black. Usually the two-humpers are all chrome. - what years?
Oil Tank / Oil Lines
-- tank - what years?
Chain Guard / Primary Cover
-- primary cover - what years?
Seat and Seat Springs
-- Look at Murph's 1962, as all three of Dave's bikes have the standard two-people seat, not the optional solo seat
-- ????
Front Brake / Clutch
-- front brake drum - what years?
Now look at Craigslist Photo 4
Chain Guard / Primary Cover
-- chain guard - what years?
Engine / Transmission
-- cam cover - what years? (this is important, and I've included a blow-up photo since it'd hard to see in the original)
-- air cleaner - ???
So - your conclusion (fill in the blanks): This is a 1961 engine in a 196__ or 196__ chassis, with 1970's _____ and _____, and at least one 196__ part on the engine,
and some custom/chopper _____, _____, and _____.
The "structured methodology" of going through the AMCA categories and comparing the subject bike to known good examples makes it pretty easy to analyze a bike. The AMCA categories may seem a little bizarre at first, but they work pretty well for any year, make and model of bike.
Dave