Gearbox difference - 912s and 912ULS

1. For my application (Gobosh G700S LSA) the part number between the ULS and S is the exact same.
2. If buying a new gearbox, specify that it should be a certified gearbox going into an S engine. You will get some sort of documentation that says it is a certified gearbox.
3. If buying an overhauled gearbox, I will have to check that the "serial number" is from a certified gearbox.

they are exactly the same between the certified and non-certified, just like the everything else on the engines. The certified parts come with a Form-1 authorized release certificate and cost more money.
Please note: Many certified engines use a hydraulic governor so the gearbox will have a different part number than the fixed pitch gearbox (just the propshaft is different)
If I understand your question correctly; you want to use non-certified parts on a certified engine? this will void your certification.