Hi Antotny110,
Tried this when I had a P38 a couple of years ago. Overfinch do them but are very rare and expensive. There was an independent land rover specialist selling them a couple of years ago (sorry can't remember their name). Rang up and enquired - told it was an easy fit. Parts came very quickly (basically looked like a defender bench seat!). NO fitting instructions, no seatbelts, bolts anything. I was a bit up against the wire for fitting it time wise. Started stripping the P38 and soon found it was going to be a complete bast***d to fit. Range up and then was told very difficult to fit - managed to get refund but they were a bit off about it (I love the British attitude - sell something that was a carp product, didn't fit, not fitting instructions, poor advice etc......).
Anyway, moral of the story - research very carefully before you start pulling your P38 apart..... Oh and also might be worth checking with insurance company to see if they will cover it before fitting.
regards
Darren