Did you use the 2 part liquid epoxy plastic mixed at room Temp and just poured into a mold, or was it an expandable Foam, like you buy in a can to fill in voids for insulation purpose? The stuff I'm talking about does expand a little when mixed, but not like the spray can foam does. It's also a lot harder like a piece of wood when cured, but light weight. They cast in Steel Inserts so you can actually bolt on the engine parts just like a real engine. With Casting a Part, you could also maybe mix in strands of fiberglass like they do with Cement today to make it stronger.
There is Molds for long term production for making many parts being made as in a business use and there is molds for one off's that can be made cheaper. Lot's of stuff in Scrap Yards that can be adapted.
Off Topic, but google "Snow Glider" hit photo's and look at the Yellow one once made in Russia with a Rotax 447UL! That's a neat idea, maybe use a 25hp Brigs & Straton.
In a message dated 2/11/2017 7:18:18 P.M. Central Standard Time, Q-LIST@... writes: