I run a Williams box in my valver. Ever since I knackered my 16v gearbox when the driveshaft shed its bearings. Its a straight fit though, no problems fitting the Williams box to the 16v lump.
Anyway, the Williams is *definitely* a longer final drive. 1st, 2nd and 3rd seem to be closer and shorter, 4th the same as on the 16v, and 5th is longer. Thats what it feels like anyway, I may be wrong. AFAIK the 19 box is also longer final drive than the 16v but the spacing of the ratios is more similar to the Clio 16v cogs?