Quick and to the point...
The 325xxx NHT used in the S2"E" rolling chassis is a tremendously different variation of NHT with minimal compatibility with the prior 300000 family.
It is easier to list the parts that have carried over from the 828cc series, which is again different from the prior 200000 750cc series.
Head with internals
barrels with lifters
piston, rods
camshaft, timing chain
ignitions points assy
some other components are possibly useable only by re-engineering and machined modification
The primary and gearbox are also vastly different and not easily converted for use on earlier versions. Only the clutch, shafts and gears are carried over from earlier models.