Rover 1.6 or 1.8 K-series engine, 5 speed XR4i gearbox or Caterham 6
speed gearbox. The differential is from a Ford Sierra XR4i unit

thats all i can use? or will there be more complications ?

is that what you have or is that what you plan on using?

good call on the k series engine, but that wont fit on the xr4i box. i think its a mt75 without a removable bell housing so thats out unless you use a ford engine.

the 6 speed is the one you want i thinks that deisgned for the k series

differential is fine as long as its a good ratio, i think the xr4i has the lsd didn't they?

some one will probably be along to correct everything i've said now but welcome anyway

or 1.4 K series

Titan do a bell ousing to match a K series to a type 9 gearbox

paint does a smaller avatar!

if it uses a sierra diff, any 7 inch unit will fit. the xr4x4 had a LSD. not entirely sure on the xr4i.

more details on your project might help us tell you a bit more specifically what you want/need.

tom

1.8 with 6 speed box imo.
More power = more