Not sure what power he is running but if you converted to the Focus 1.8 flywheel you open up the possibilities of running an IB5 box which may suit his car a bit better. The shift is a bit better (MTX-75 box is reknowned for not liking quick shifts) and they are a lot more available because they've been on pretty much every FWD Ford model in one guise or another for about 20 years (Mk3 Escort was 'I think' one of the first to use the B5 gearbox and they have all been developed from there - so a S1 RST LSD box could be one to look out for). Not 100% sure they are all bolt on fitment mind but if you've got a lot more options chopping and changing ratios in the B5/IB5 boxes than you have in the MTX-75.

Only problem is that they don't stand up to massive amounts of torque in standard guise (certainly the case with the IB5 fitted to the 1.8 Focus which tends to start struggling up around the 170bhp - 170lb/ft mark) but then there are plenty of companies who can strengthen and uprate gearboxes and clutches (just don't use CTS because they are shit! )