The drivers side fenderwell is plastic and the passenger side is metal. Why? The plastic fenderwell says made in canada.

I've seen several cars like this. I've heard that when the line used what ever they had. If they ran out, some cars had one metal and one plastic.

Im started pulling the 307 tonnight to replace with a 350 street motor im building. Im going to be restoring and painting the engine bay area. can that plastic fenderwell be painted?

Not with much success. Polyolefins (plastics such as polyethylene and Polypropylene are inherently difficult to paint because of low surface energy. There are adhesion promotors out there to work with certain paint systems, but usually result in a compromise of paint properties such as hardness or chemical resistance. The best suggestion for painting Polyolefins is to flame or corona plasma treat the surface of the plastic. This doesn't mean that you go at your plastic fender with your Bic lighter. You can check-out this site if you are more interested: http://www.enerconind.com/treating/how3DTreatingWorks.html

Danchuk sells a set of plastic fenderwells for 169.95.