Hello Trent : One of the biggest parts of the Phase III was the different torque converter I do knot know is the driven clutch was different that the standard one used on the RST 340
I sold two Tri-sports as parts to a member in Southern Illinois and in that 1200 pound crate were 2 sets of exhaust pipes and 1 after market set. And there was two roll bars and some kohler engines. One of the frames was a two tube main frame like they used on the Phase Three Racer. I sold that trike to Jack Harkey in 1973 and I sold his wife a Street Legal 340 in 1974. I bought the RTS and the Street legal back from him in 2002 and I found out that his engine was a 440CC Kohler with single carb.
I restored the Street legal did a lot of changes to it like 10 inch rear wheels and eventually went to 10 inch brake disc and dual piston calipers. I had new upholstery made in Blue & White & Silver added more lights front and back plus air horns and a lighted whip antenna.
I never sold any of the Phase III Racers. I did buy one RTS here in Portland that had a modify ed Kohler out of a snow mobile that had twin carbs and it had the expansion chambers and roll bar. That engine is the only one I ever seized up. That trike was in the big box that went to Illinois.
Yours looks super nice and all of us welcome you to the great OldMiniBikes forum and please sent more pictures of all parts of the trike like the bottom to show the frame and the brakes .
Even as a dealer I was on the west coast and only got any information from the local distributor so even after all the years there is information lacking.
Steve