disc brake rotor question

I currently have 1973 Gia disc brakes for my sppedster and would like to know what the difference iss between front and rear rotors?
A friend has offered to sell me another set of rotors cheap and if I can replace my rear drums with these I will buy them.
What are the differences?
Any comments?

John

The front rotor rides on bearings. The rear has a spline which fits solidly onto the Drive shaft.

Depends on your setup - late model IM's with 914-4 rear disk brakes use a "hat" type rotor that attaches to the rear hub and is replaceable. It's not a simple switcheroo - buy a CB Performance rear brake kit for your car and it will have all the right stuff, and get a 4 psi pressure retention valve in the bargain.

Sorry I can't help you with that, I'm only working with BIG stuf in that aria, and in that aria, the 'tec' is not 50 years old, not a small problem with us. BUT I'm working on it.