Welding the split collar to the frame is an excellent idea. If the frame isn't one you want to leave original it would indeed make remounting the engine much easier.
I looked at the Seal Sociable again. It is apparently a 4 passenger body and has a 1,000cc engine originally. The body would be easy to reproduce or in the in the case of the Kindalikeawhizzer Sociable a mahogany upper body crafted to fit the canoe lower.
Better clear the deck at Bike Camp this summer. Finish off the Tri car which really just needs the final touches and then we can have a Sociable Time.

Get the big beer cooler out this summer. I sense a lot of creative staring happening this year.
Steve.