| Date | Item | 337 | STC |
| 1985-01-11 | Precise Flight SVS | X | X |
| 1992-12-16 | Sensenich Propellor | X | X |
| 1992-12-16 | Brackett Air Filter Assembly | X | X |
| 1993-04-14 | II Morrow Flybuddy 820 GPS | X | X |
| 2002-06-19 | Engine Monitor Insight GEM 610 | X | X |
| 2002-06-30 | S-TEC System 40 | X | X |
| 2002-06-30 | Century NSD-360A HSI | X | n/a |
| 2005-10-12 | Nose Bowl Split Kit | X | X |
| 2005-12-26 | Precise Flight SVS Upgrade | X | X |
| 2010-01-11 | Garmin GNS 430 | X | X |