Well, I've got 3 little ones that'll spend some time in the back. I got out the tape measure as I get ready to buy a rear seat and start sorting out the cage etc.
Anyway, I saw this seat 48in bench:
EMPIUS.COM : 2008 Catalog, Page 286 - Off-Road
Looking at the dimensions and playing with that tape measure

It looks like it would be 'tight', but doable. presuming that I mount the seat off the floor a little, it would seem that the seat wouldn't extend out to it's full 48" until it was above the bed rail. It's only 41"at the base.
How tight is the 42" on the sides? I know, it's probably pissing in the wind here

but I thought it was worth asking before I buy a 42"
Thanks.