An old trick is to use the middle cog on the cluster and shorten the chain. You need a handbrake because it will still be freewheeling. A one speed coaster brake wheel should line up also. The sprocket on the one speed may not use the same chain as the freewheel. I've swapped out wheels that way and they have always lined up. You might add washers to get a little alignment correction. I also used one other trick. On the one speed wheel, the locknut for the bearing adjustment could be removed and still work while giving you a little less distance from the frame, IF your bearing adjustment is threaded also. That locknut is the width of a couple washers if your wheel has it. I might paint Saturday if it isn't too windy.