If it makes sense in your timeline, its a lot easier to find out you have mechanical problems before you paint everything up and carefully assemeble it.
When I did my SF112, it was a non running (and of course non driving) tractor when I got it. I had the engine rebuilt and did bolt it back on the bare frame after to run it.
But then I sent everything out to a body shop to paint. Assembled it all and went to drive it. CLICK CLICK CLICK in the tranny.
Had to pull it all apart and found a gear missing some teeth.