Looks like an XP skid and track. I did the same to mine last year. I did a 154, looks like you've got a 163. I'm very happy with my conversion so far this year.
Shannon is a whiz @ fabrication! (You should see his XP based asphalt sled with a welded together triple - 800HO based, with fwd facing carbs & rearward triples exiting under seat shell!) Clean... I believe he had a friend cut out the "side plates" from templates he had made. Last time I talked to him, I think it had a ported 800 W/Crankshop Twins.