I've used belts out of a '99 Ford F-150 extended cab on two different '40s. Both mated up to other junkyard seats, from a Hundai and a Toyota Solara. Key was to work the shoulder strap off of the rollbar.
The '99 F-150 belt has a cover that come with the retractor, for both sides. One bolt holds the whole thing to the pickup's rocker panel. One bolt holds the ceiling connection to the pickup roof. Got'em for $50 bucks for the pair. Sorry, I can find no pics that show the detail. I can take some Monday, if you can wait until after my turkey hunt!
I pulled two sets yesterday from a local pick and pull. Both came out of older chevy vans. Easy to pull w/out any damage to the covers. Just need to make some tabs and weld them to the roll bar. Cost $20 for both sets.
try to find a toyota car of the same year the belts on the passenger side will be in good shape you will find the right colors as well that's what I did when I had my 40.....also used the rear middle seat belts for the jump seats....very cheap way to get oem...