I think the post 92's actually had smaller line size, 7mm from memory as apposed to the pre 92's 10mm line size...
The price difference I expect is the post 92 run an "in tank" electric fuel pump that is located at the bottom of the fuel pick pipe which it part of the sender unit so that may be the reason for the difference in the pricing, however unjustified.
Just a point to be aware of here.... You will more then likely need a higher volume electric pump over the STD so if you go new try to get a sender without the pump. It might bring down the price a bit if you can, but check it out with your blokes to see what combo they intend on using first.