I could find another neck board and I checked tube type into the manual.
In order to understand the tube compatibility between a MTC 90 and a MTC 900 I compater the MUTER adapter needed
MTC 90 -> 813
MTC 900 -> 815
if you check the adapters schematics into the manual (see andysarcade.de) you can see they are completely different, so TUBES are not compatible at all.
So I have these choice:
1) try to understand if it's possible to biuld a neck board "ad hoc" for MTC90 with MTC900 tubes. Then the question is: what about deflection yoke?
2) vernimark, use a MTC900 and not bother us anymore with your philology
probably I'll chose "2"