Can anyone tell me what the ideal dimensions for a front mount intercooler would be? What stock intercoolers for other cars would be a good fit?

 

It depends what your setup is(what turbo, etc).

 

The external dimensions are not as important as the actual performance of the intercooler. See the Spearco charts in the Turbonetics catalog.
http://www.turboneticsinc.com/

Higher efficiency = better cooling
Lower pressure drop = more boost for your buck

Also note that smaller internal volume = better boost response, but larger internal volume is better for efficiency and pressure drop, so you need to make some type of compromise. Above all else, the intercooler needs to fit in your car.

If you are looking at junkyard intercoolers, taller is better than longer, but longer will still work OK. Thinner will heat soak less at a standing start, but thicker will work better for a road course. Try to stay away from anything thicker than 3.5" for a street car because you need a lot of air to flow through the thicker 4-4.5" cores, and that's not going to happen at legal street speeds.