This site can help you in your search with all the spec sheets you would need.After reviewing the engine mounts I made from the KB2 plans I am about convinced that .065 wall with cross tubes for bolting on the cheek plates would be sufficient. If I could figure out where to look I would look at the strengths of 2 inch .065 wall 4130 vs 2 inch square 6061 aluminum tube.
Don't get stuck at the depot or supermarket without the materials you need for your metal fabrication. Order from the best.
With over 21 years selling metal online, we offer the best service, selection, and knowledge. Free MTRs, no cut fees, fast shipping!