Not sure if its the route you wanna go but I just ordered a set of seats for my dad's 65 dart wagon from a website that sells parts for step vans. Theyre a really nice lookin seat and pretty comfortable too. And you definitely can't beat the price and they they come with the seat track. You'll just need to make your own brackets which isn't very hard at all. Here's the website
http://store.stepvanparts.com/LO-BACK-VAN-SEAT-F7100S.HTM