My trailer came with 12inch tires. My mods were a longer tounge and a simple racking system.

12 inch tire (with rim) cost about $40 each at Wal-Mart. I don't know if they will fit the lug pattern on your trailer. That would be the main issue. Moving the fenders wouldn't be a prob. Get one from Wal-Mart, see if it fits, if not take it back and only time has been spent. They had 4 and 5 hole rims at the store I shopped when I bought my spare.

I was told that 8inch tires are fine for shorter trips. I went with the trailer that has 12inch tires simply b/c it was on sale at the time. I guess 8inch tires wear faster due to more rotation and higher heat. I don't know of much else that would be different.