Koni stuff is good sh!te whatever you buy. As for correct for a cab I'm not sure. The cab is heavier than the tn top so you may want higher poundage springs. I would advise speaking to someone like TSR or one of the other tuners to see what they would recommend, then buy it online and have me fit it. Mwahahahahah!nick
http://www.weitec-suspensions.co.uk/uk/products/coilover_uk.htm
The koni kit will be fine and can tell you 100% that all mk1 susp will be ok, cabrios are the same.