Is there an understanding P car model numbering for dummies guide out there?
Uhmm... maybe?
I've got it all in my head. Probably helps I've been P-car nerd since I was like 3 years old.
For the modern, relevant recent stuff...
1965-1989 Carrera is just "911" (save for the 1989 Carrera 4, which was the "new" car, and is a "964") and are denoted by submodel, front hood length, engine size (911 S/T/L/SC, 2.4/2.7/3.0/3.2, longhood, short hood)
1990-1994 Carreras are the 964
1995-1998 Carreras are the 993
1999-2004 Carreras are the 996
2005-2012 Carreras are the 997 (append a .1 or .2 to denote M9x motor or DFI.... the .1 is up through 2008, .2 is 2009-2012)
2013-2017 Carreras are the 991 (with .1 up through 2016, .2 is 2017)
For the Boxster/Cayman:
1997-2004 is Boxster only, those are 986 (.1 through 2002 I think... .2 had glass rear window, minor facelift)
2005-2012 is Boxster and Cayman (Cayman was new for 2006), those are 987 (with .1 up through 2008, .2 is through 2012)
2013-2016 is 981
2017+ is 718