you can buy a complete base and swivel but very expensive,people just go for a swivel as you have a base already,there are different types,most people seem to reccomend fasp swivels which is like a circle of ball bearings for the swivel and are great quality i think c-m-c do them,there is another type of swivel with a big centre bolt but people avoid these as it rocks on the bolt when you are sitting in it,
any t4 seat ?? or any seat in general???
t4 seats and bases are different think up to 1997 then 97 to 03
if you were fitting aftermarket seats then you would have to modify as all seats are different bolts spacings/fittings
cmc [cheshire motor caravans] also do a base with a safe built in with a swivel but I wish I never bothered.it rattles like hell and is a centre bolt system.I agree that its best to buy fasp swivels and fit them between the seat and your existing base. not cheap hence so much interest in second hand ones.www. outdoorbits.com are worth a look.T:
I went for CMC bases after reading complaints of FASP swivels not fitting properly; quite a few people have to spend hours filing to get them to fit, indeed there were a couple of forum members who had swapped their FASP bases for CMC ones and were happier with them. Also a friend of mine who drives a big motor-home had a set of FASP swivels on it and one completely came apart when she was driving it which was the deciding factor for me.
That said, there is a slight rocking on the centre bolt (it's very, very slight to the point I'd say it was completely negligible, but maybe that's just mine) and the safe did rattle like mad, but I stuck some lining carpet on the back of the front panel of the safe and it doesn't make a sound anymore.