advice on painting over rust

I am now the proud owner of a 1991 ford mustang 2.3 four cylinder monster!    The car is named "the point five oh".  My sixteen year old is thrilled--he was raised on "roadkil" (the show, not the food) and my wife thinks the seats are more comfortable than her fiesta st!

The car has a certain, well...look.  We wanted to preserve it, so I was thinking of putting a coat of clear over it.  Does anyone know if the surface rust will just eat away under the clear?  Also, has anyone rattle canned clear on a car?  I rattle canned white primer and it came out pretty nice.

This car is replacing my beloved focus svt,  which was t-boned three weeks ago.  This is the silver lining to that cloud.  We got the car from vermont.  The water temp was sketchy the trip back to Maine, and the battery wouldn't start the car after being turned off in our driveway.

We are thrilled.  ? What are the rules for the challenge?  Is this a gastropod?  A whole new vista may be opening!

Yes, rust will continue to eat away under paint/clear. 

Exterior rust spots are often (usually) early stages of pinholes eating away from the inside, in which case your only realistic options will involve repainting. 

Rust aside, you can clear over the old paint, but it will lose much of the character of the car. Plus you'll have to remove all the oxides from the surface first which could breach the top coat.