There is a lovely website dedicated to the little Harley Aermacchi's I ran across through the Aermacchi Yahoo group. Take a look here: http://msolisvintagemotorcycle.com/home.
I lifted all these photos from there, but I know he lifted them from elswhere as I've collected some of the ones he has over the years myself. The bike above is pretty much what I'm talking about for my bike. They made a few different race bikes over the years and this particular one is the CR for flat track. Most of the CR's were hardtails. I would certainly like my bike to be a road going version and I have no desire to cobble up an original CR. That said, If I could do mine up to look like the one above with a few exceptions, I would be quite pleased. Brakes and lights would be the most important, clearly. The lines on this example are perfect. Not an easy task for a Sprint. Once you compressed the springs of that saddle, you would just stop if you tried to slide onto the P pad. It looks so much better this way, however.
The P pad here is oriented properly for function. Looks goofy, but it functions.
Of course I had to include this one with the green sparkle seat.
Mert Lawill at the Cow Palace.