I went to a friend who is moving house; he had about eight scrap bikes; I chose a shopper and a BMX.
This could be made from one bike but I like the height and open frame of the shopper and the tough wheels of the BMX; so I used both.
The first action was to take the wheels off the shopper and then remove all cables and brakes.
The shopper tyres were flat and as I don't need brakes it was ok to use the slightly smaller BMX wheels; and they look good.
So I put the BMX wheels on the shopper frame but I needed to slightly widen the forks and the rear triangles by standing on one side and pulling the other side up, not too much though; also I had to file out the dropouts on the front fork a little to accept the marginally wider axle.