I have a 69 KE10 and it has only front seatbelts. I think rears were available as an option.
Personally I wouldn't be fitting seatbelts if I didn't have to.
Yes mate, I've seen 15's at the wreckers and owned/own 13's and 14's. I think they may be 4.5 to 5' wide. Easily widened by a competent welder/wheel shop just like having yours welded and redrilled. Having said that, 4.5 - 5' wide is plenty if you plan to use whitewalls as they're not available in decent widths anyway.
I'd probably go something bigger. I've got a 13cfm 15 amp compressor and it runs everything well but it did struggle a bit with a larger rattle gun. It's an ABAC brand, 3HP, 50L, 13CFM I picked up for $550 down from $799.
I'm going to go out on a limb here and say they may well be factory. I think some of the brochures I have show them fitted. I'll have to have a look and see if I can dig them up.
$1000 for the set. Only joking, they should go in an envelope so postage should be cheap enough. They're free but let's say $10 for postage and my time?
I should have what you're looking for. I'll see if I can dig it out of the shed, I'm just hoping I didn't bin them. Perhaps you should send me a PM sometime to remind me.
If it doesn't require a RWC snap that sucker up and just drive it in to the ground.
I snagged myself a twincam AE82 for $235, was $250 but I found $15 in the ashtray. Sure it's got a few things wrong but i drive it to and from work and it sits in the sun all day. I couldn't ask for a better car for such duties.