[bmklawt]

I had to do the same thing to a Doodle Bug I'm making with an "A" axle, I would cut off what you can with a cut off wheel, the thinner the cutoff wheel the faster it will go, and then use some 40 grit flapper wheels to sand down the remaining. The flapper discs will make quick work of cleaning up the welds, I would think you could get the job done in less than an hour.

Flapper disc, Neiko 11142A, 10 for $17.00 on Amazon