Nice to have another sidecar racer on the forum! One of the bikes that influenced my own build was the lovely girder rigid 6T of Sue & George Derbyshire who bought their rig out to NZ a few years back. I had a historic (read fairly battered, featherbed based) norton atlas rig and after seeing their bike decided to build a proper old school rigid albeit with just the one camshaft in the correct place behind the motor
Hope you get some pleasure from your new acquisition over the UK summer while here we're in winter rebuild mode with temperatures plummeting down to the mid teens (in celsius)