Ive been looking for a used alum trailer........guy around here has one, good shape, great price but it only has the 5 bolt axles......I wanted to go to 6 bolt......I can pick up a pair of axles complete with springs and brakes for like a grand and I could sell the old stuff......anyone ever do something like this?

Yep. I just did it. Complete axles (two tandem) with brakes, springs was slightly over 5k. Took about 3 hours to replace them.