PORSCHE RACING HISTORYMike Tillson (USA)
1973 : Sebring 12 Hours - 3rd in class
4 February 1973 - Daytona 24 Hours - World Championship for Makes
| No. | Car | # | Class | Drivers | Entrant | Pos | Class | Grid | Notes |
| 89 | Porsche 911 S | GT+2.0 | Mike Tillson (USA)/Al Holbert (USA)/Dieter Oest (USA) | Holbert Porsche (USA) | DNF | 42nd | 213 laps |
24 March 1973 - Sebring 12 Hours - Non Championship Race
| No. | Car | # | Class | Drivers | Entrant | Pos | Class | Grid | Notes |
| 91 | Porsche 911 S | GTU | John Bently (USA)/Mike Tillson (USA)/Harry Bytzek (CDN) | Holbert's Porsche-Audi (USA) | 10th | 3rd | 43rd | 198 laps |