The swap that you mention is simple. Open the Spyder trans and swap the RP from one side of the housing to the other. Everything ought to remain as is, no re-fitting or adjusting needed. If there are heavy duty side covers on the Spyder trans, keep them, otherwise just take everything from the fulcrums outwards from your trans and use them on the Spyder trans. No worries about brakes or axles/tubes/brakes or anything. It's a simple one for one swap. You can score a gasket/o-ring kit and all that for the assembly anywhere on the net.
I did the typical short axle conversion on my swing axle and it was like working on a Model T, Easy Peasy. What you're planning isn't that much harder.