Got a second springer fork center tube? There's your swing arm pivots. Cut the two fork tubes to length, sleeve them with a bit of pipe, zip zip with a weld and there ya go, rolling down the lane.
Love the main lick in Riff Raff. I saw them a few years ago in Chicago. They were great. 3 hours non stop. You knew every song they did and they had every piece of stage props they've used through the years, from the giant Angus statue with glowing eyes to the two story inflatable Whole Lotta Rosy, cannons , locomotive, a huge bell Brian Johnson was swinging on. You could tell they were having fun too. Underrated for years, Malcolm is one of the best rhythm guitarists of all time.
Carl.