1920s Harleys

In my latest diorama I want to put an old Harley from the 20s in the scene.The closest that I can come is using a 1/18th diecast by Maisto.I plan to put an 09 engine in a 36 model and modify the 36 to look more like a 1920s bike.If anyone has an easier solution please let me know.I dont mind scratchbuilding if I have to.Cheers ! John.[:)]