Evan added a post in a topic Sbfa General
Cool! Someone found my site!
The 20 figure is an estimate; I'm working a few sources at GM to nail that down to a firm number. My guess is it had to be just as scarce as the Aero Astro was.
And you're right - as Chevy exited the HD business in 1980 and the SBFA N-series came in '87, a Bison SBFA didn't happen - although with a swap of badges and grille inserts, it could be...