Me..I made something similar about 12 years ago for a P39 racer using a 150 four stroke..Mine was made from solid aluminum, not bolted together...still have the piece around her somethere...Way too heavy, even though it was milled out on the sides and bottom...
There's another way..
I made a 10" long extension for a 3W 70 twin to be used in a Nemesis F1 scale racer..
Threaded an aluminum tube to the front of the crankcase, made a long shaft that screwed onto the crank, put a bearing in the end of the tube..Worked fine, the engine wasn't quite strong enough to win....