I'm going to use jacknuts. I found that Chevy had used these along with some very nice stainless bolts on a 79 (possibly 77 or 78) Chevy van I found in the junkyard. I checked with my local dealer and GM still sells the parts. What's really nice is that the exposed portion of the jacknuts is vinyl coated and the bolts, in addition to being stainless have a small nylon washer so everything is protected from damage and the door is sealed. NAPA sells the jacknuts also as part # 665-1059 (
http://www.napaonline.com/Catalog/Re...Dp%3d3%26N%3d0). As stated above, I also believe the bolts can be purchased from GM if you like them.
Here are some pictures of the parts. These do require larger holes in the doors, and this is not original. Incidently, my 69 came from the factory with sheet metal screw/bolts, which did pull out, and nothing between the mirror leg and the door. I believe later models may have switched to bolts.