The Early rod change boxes are all shorter than the cable change versions. So an Escort Rs2000 one would be your best bet and probably the easiest to obtain.

Jano sells the clutch for them too, as they are a bit of a fruity size and a Focus RS one won't fit in the box without a bit of grinding and a 3 of those gearbox spacer plates to push the box away from the engine. You can see this on QplateRST build thread - the Blue Zetec Mk2 Fiesta.