Thank you @ObjectiveAway , @Rick !
The gearbox was removed due to the failure.
Clutch has become super hard and hammered into gearbox by torsion shocks while clutching.
Gearbox has become solid, concreted.
So sorry, only 5th swap is not possible.
Calculating the final ratio of:
ESY 5th gear 3,65 (4.06 * 0,9)
with
ETD 4th gear 3,87 (3,87 * 0,93)
and they are quite similar revs
and there is room for
5th gear 2,86 (3,87 * 0,74)
There are 190 mm and 200 mm diameter clutch
versions of 085 gearbox.
Are they different - not compatible?
(I have 190mm clutch)
I consider DHB, DKF, DQW, DXP, ERD, ETD, FGF