Matt, many trailers have axles bolted on. And, many cars were partly bolted together for years. The wings are bolted onto airplanes. I suspect that bolting will hold. It will also let you adjust things if spacing isn't right the first time.
Once you get the trailer rigged exactly as you want it, you could use castellated nuts (drill a small hole in the bolt for wire or a cotter pin), use LocTite, or get it welded.
Doing what you like is FREEDOM
Liking what you do is HAPPINESS
I spent most of my money on airplanes, whiskey, and women - and I'm afraid I just wasted the rest.