100s box ... No.
reasons.
Bolt pattern to block is for a twin cam, which is different to a sohc.
Spline on input shaft is not the same as 128.
Starter wont fit. (different bolt pattern between dohc and sohc starters)
Axles on a 100s have an inner CV joint, not a tripode joint inside the diff like a 128 and regata 85s
physically it's a lot bigger, and will foul on the bodywork of the 128 (where the gearbox mount is touches the sway bar)
85s box, yes and no.
85s is 1500, it uses a bigger clutch, different ringear and different starter motor.... these can be overcome with mixing and matching and some machining. 85s also has different sized tripode joints (larger than 128) so you would need to fit these to the 128 axles (which again requires machining to the axles to allow these to fit) 85s box will also have clearance issues where the left gearbox mount attches to the gearbox, but this can be removed.
SteveC
