From a BAT posting by Rennbuffet
"The SWB 911 is a special car, the original, pure design of ‘Butzi’ Porsche, before the wheelbase was lengthened and weight added here and there to make it more appealing to a broader audience.
Here is a fun fact, only 3.8% of all air-cooled 911s built are SWB. Breakdown is:
SWB – 16,117
LWB – 64,983
G-Body – 199,464
964 – 69,648
993 – 69,190"