R&P\'s for T3\'s (kombi) - need taller gearing

This might be a stupid question, but here goes....

I've got a 1990 (2.1 litre) T3 Caravelle 5 speed manual and was wondering if the r&p's from any of the 3 (3.74 i think?) or 4 speed (4.09 i think?) automatic T3 Caravelle's could be used to replace the existing 4.57 r&p?

Alternatively, if this is no where near possible, are there any aftermarket r&p's out there for the T3 caravelle 5 speed?

I'd like to lower the revs (give it some taller gearing) in order to take full advantage of a planned subaru ej25 engine conversion or if i modify the standard engine for more power.

From what i understand the earlier 1.9 litre 5 speed had a taller 5 gear (0.77?) that i suppose i could use to help lower the revs on the freeway, but this doesn't help the other 4 gears and i understand you can change the wheel/tyre size to help out, but this only helps to a point

Thanks

[ Edited on 18-9-2006 by kombi kountry ]

[ Edited on 18-9-2006 by kombi kountry ]