I just completed an upgrade to this engine. I have worked on a lot of PS-2 4-6-0 and 4-4-2 Premier engines but never upgrade a PS-1 version. I finally got to see the 33.7mm flywheel that the kit has a tape for THis engine also has a unique drive assembly with a rubber bushing between nylon drive teeth to turn the gearbox shaft.
Because of the close fitting shell and nature of the motor mount I had to custom wire the engine harness to route and hide wires. This engine took me all day yesterday to complete. Solid 10 hours with some breaks and lunch. Only 3 billable hours.
Pictures attached. G