whats the differance between the ercoupes of the 40's and the alon aircoupes of the 60;s?

Answer 1

I believe the Ercoupes had fabric covered wings, while the Aircoupes had sheet metal skins. The Ercoupe started life with a Continental C-65 engine, and the Aircoupe had a more powerful Continental C-90 engine.

From Wikipedia... "The Alon A-2 and A-2A Aircoupes were much improved upon models of the original Ercoupe which differed from it in several ways. The Alons featured a sliding canopy, a more powerful 90 hp (up from 75) Continental engine, separate bucket seats and a much improved instrument panel."

Answer 2

In addition to what jetdoc had to say the Alon had rudder pedals. The Ercoupe was steered on the ground with the control wheel like a car and the rudders were connected to the wheel as well.
Forney made them in between Erco and Alon, and Mooney made them last of all. Mooney called it he M-10 Cadet and it had a distintively Mooney tail.