I don't know how your seat mounts are laid out, but on my '62, it originally had fixed rear windows, with sliding middle windows (perhaps indicating that it was never equipped with the third row seating). The mounts in the floor for the third row are there.
In the middle row, the mounts for the abbreviated second seat are there, but there is a second set of mounting recesses for the full-width seat that was usually used as the third row.
Meaning, I can take a full-width third-row seat, and install it as the second row, and then keep the rear cargo area useable.
The guy I bought my truck from had a '60/'61 Suburban too, and he was driving that one. He had the short second row seat in his truck, and no third row seat.
He sold me the third row seat for $100 extra. I noticed the mounts in the truck I had just bought, looked at the seat, and we set it into position.
He looked amazed, and then we looked at his '60. Sure enough, he had the additional floor mounts for the full-width seat in the middle position too! He asked if I'd like to sell that full-width seat back..."Nope!"
Just something to keep in mind while you're looking for seats. A full-width seat will bolt in the middle position.
My Suburban also has a pick-up front bench, rather than the 60/40 split. I've owned it for less than a year, and I've found a set of '59 Panel buckets that will look right at home up front, but I also just found and bought a stock 60/40 split. My point is, in less than a year, I've found seats for my Suburban, as well as 5 sliding window latches. Counting the $100 I spent on the rear seat the day I bought my truck, I have less than $350 in all my seat--including buckets--and window latches. The buckets were in excellent shape, the split bench needs a little work, and I rebuilt the rear spring beds, but they were all complete, not basket cases. I found really good deals, so that's less than most guys have spent, but I've also passed on seats I just didn't want to shell out the $$ for, and kept looking until something cheap came along. Same with the sliding window latches. Keep your eyes open, search everywhere, tell your friends what you're looking for, post it on different boards, and you'll find what this truck is missing. Again--those deals, those prices, 9 months of searching.
In the mean time, make do with junk yard buckets and a van rear seat.
Brad