Bob, STC must have been withdrawn. It was approved in Canada based on US STC#SA01197CE.

If you can find and obtain all the drawings &c. from that STC, it's certainly enough for a field approval. Owise, field approval based on prior field approval is doable. Just don't buy anything until you have IA or even DER line it all up. FSDO's just don't have the budget/manpower/expertise they did 40 years ago.

By the way, are you using a climb prop with the 160? 50" pitch or...?