Roger: My mistake, I should know better than to make assumptions like that.
From Wikipedia: Later in 1989, Blackaller entered a Swift Engineering DB2 Sports 2000 with Sonoma County (California)-based Pfeiffer Ridge Racing for the IMSA 300 Kilometer race to be held at nearby Sears Point Raceway (now Infineon Raceway), on 10 September of that year.
Blackaller suffered a heart attack while practicing for that race.