Grab Handles

[Times Welding]

I've got an '87 K5 with no interior grab handles. I have 4 new GM handles with covers and spacers that I'd like to install, 2 front and 2 rear. I've peeled back the headliner and found that there are flat bosses with holes stamped into the sheet metal above the passenger door, but no threads. It also appears that the factory spacer has a round boss that the bolt goes through, that extends into the hole in the sheet metal for location. So, what does the threaded section look like? I'm sure it's something that I can fabricate, but I need to have some idea of what I'm making. Also, I've seen some later K5's with grab handles installed in the fiberglass topper at the back seat. What provisions were made for those handles? Or can I just drill some holes and use lag screws? Any input would be greatly appreciated.
Thanks
Doug

 

[Times Welding]

I've been able to inspect a Suburban at a local salvage yard to see how the front handle mounts. It's not a problem. I still would like to know what mods I need to make to the fiberglass topper to accept the rear handles. Any ideas?