If you haven't already found these sites, check them out:
They have a lot of useful information regarding resin types, cloth types, etc. in their Learning Center link.
Another one is
They also have a learning center.
The last one, which I bought my material from when I made my trans tunnel (documented in my project journal) is this company:
They have good prices, and also a FAQ page.
There are big differences between an epoxy resin and a polyester resin. Epoxy resins can come in different viscosities, and can be mixed with different speed hardeners for various curing times.
There are also different types of polyester resins also, including vinyl ester types. Depending upon whether or not you are doing multiple layers of 'glass, you will need to use a waxed or un-waxed type of resin.
Also, what type of 'glass (cloth or mat)you are using may dictate the type of resin.
For my fiberglass mold work, I used the polyester resin and 1.5 oz. mat. I did also purchase some epoxy, but I have only used for attaching and gluing parts together, not as a fiberglass reinforcement.
Not to send you down the wrong path, I suggest you visit these sites and get the scoop from the manufacturers.
I also found out a lot from this board by doing some searches on "fiberglass" and "fiberglass mold". I believe that Powerrodsmike had some excellent posts regarding fiberglass work.
Hope this helps,