[Ashlandchris]

Just to give an update, following advice from many sources (mainly on here - thanks to everyone) I decided to switch to a belt drive so I obtained the option parts for a front and rear ball diff and fitted them straight into the gearbox cases. The pulley wheel kit isn't really needed and the belt runs super smoothly.
Following some threads on the shells from Kamtec and Marwen, I tried them but they are a bit short (albeit lovely shells) so I spoke to Steve Haskens (Penguin shells) and he said he can do them the standard size as he has a mold which has been corrected.
His shell arrived and is a lovely fit - will now have to post some images of my attempt at a box art paint job!!