So, here are my suggested part assignments for each of us:
Tel- Gears and maybe carbies
warranator- Crankshafts, cams, conrods, cylinder, crankshaft, and timing gear supports, maybe the brackets for the fuel tank
hi speed scrap- Cylinder heads and valve gear components
Herbiev- Bases, bearing bushes and pushrod supports
Myself- Flywheels, fuel tank support columns, maybe the cylinders and pistons
As far as materials go, I would suggest making components requiring a lot of milling to be made from aluminium, cast iron for the cylinders and piston rings and steel or brass for the flywheels and gears, but I'm open to suggestions.