the way i did my mount is basically a rip off from the 'barry' mount i took 2 pieces of 3/16 steel and sandwiched them together to make them thick then welded them together to make one solid plate. the plate measures 4 inches wide by 8 inches long. the steel can be bought at ace hardware home depot ect . drill 4 holes in each corner of the plate and make sure the holes clear the frame this is where your going to shove your bolts thru. then for the bottom i used two 4 inches long cuts of angle iron layed under the frame with 2 holes in it to shove the bolts thru. an extra step i took at this point was to lay rubber on the bottom of the plate of steel and 2 pieces of rubber for the angle iron. after the plate was secured i found some scrap bike frame that the pipe were the same size as the clamps on the engine and cut off 2 sections at maybe 6 inches long. took those 2 pipes and loosely clamped them into the engine then took the engine into the frame on top of the mount and sized everything up,then welded the 2 pipes to the mount.
ive used this same design for 4 bikes of my friends now and they work great, there are tons of different ways to do one of these mounts and im not saying mine is the best,but this is how i did mine and i hope this helps