Hi Jon,
I have two 54's one beige and one texas brown, both have/had the tan leatherette interior. The carpet should be oatmeal and Spirit of the 50's do a nice line in the original german square weave material.
I believe the headliner colour is beige grey but someone may be able to put me right on that one.
As for retrimming the seats, Karmann Konnection do some nice covers which you can fit yourself quite easily.....over to you Jules :lol:
John