The tongue can be turned around the webbing by folding the webbing sideways  back on itself in the tongue slot. This might help with initial setup.
I got my belts rewebbed by seatbelt solutions and they are lovely and original but i soon realized that being tightly strapped in wasnt what i wanted in the capri so i put inertia reels in the front. They are much more comfortable and also the passenger doesnt have to stuff around with them. So now my luvly belts are part of a growing list of original bits tucked away in the shed.

I should also mention that there was a change to the part number for front belts in May '71. Not sure what this was, but maybe something to do with ADRs at the time?

Thanks for the tip Ron. That could be the issue with my belts. 
 
In terms of part numbers I've noticed that there was a change to seat belt tongues and buckles (decals) at some stage during. My August 72 model has buckles with the 'Press to Release' decal on the buckle as opposed to the silver decal with the blue circle (another members mid 72 model has the same). The other difference is the tongue on the later models doesn't have a riveted on reinforcement piece. 

Bump