If it was my money, or wagon, I'd just change the bolts and continue to use a spanner - which is exactly what I did on Saterday!
It saves any potential detriment to the flange (I have seem some disintergrate when welded incorrectly - not just LR ones either) and makes swapping bolts easier should the need arise (like kerplunked theads, as mentioned).
Just a tuppence
cheers
8)
Eeyore