You're typically going to need a tire like the Karrier ST235/80R16 Radial Trailer Tire - Load Range E # AM10248 to pair with the # AM20757, which have a section width of 9.25". If you can provide the overall size of the tire, I can provide better direction on this but typically a tire with a 6.5" section width will not fit on this wheel. view full answer...
I am not sure what the key you have looks like but I can confirm if you have a Global Link Lock with a G-346 key code the Replacement Key for Global Link RV Locks part # 295-000072 will work. view full answer...
The Sailun S637 tire is sized ST235/85R16 which can fit on a 6 inch wide 16 inch diameter trailer wheel like the # AM20758 that you referenced. view full answer...