Atlantic British or Rovers North both have the correct bench seats - the ones in it are not "Land Rover Correct" the bottoms may be - but the back rest is certainly not. Here is a link to the RN seats - note they are in the Series section - http://www.roversnorth.com/ProductDesc.aspx?code=PLB711
You want to check both sites to get the best prices. For more options on pricing the cool kids are now buying stuff from LRSeries.com - here are theirs - http://www.lrseries.com/shop/product...h=bench&page=1
Note pricing is MUCH better on LRSeries - but shipping can be a killer.
Also, as far as seatbelts RN and AB have them as do LRSeries
I am sure you can get two benches on each side of the truck for seating of 8
For Rollcage - the post above says it - it is spelt Tithonus - either way a custom roll cage will be needed if you decide to go down that path.