Very helpful, guys! I have watched 3 of the 4 links (still have to watch the second Gibson 63 one). I've learned a lot - most of all is how much
more I still have to learn! I've been wrenching for a long time but body work is a brand new area for me.
Not only am I on a learning curve, but the old truck is not an easy project to get my feet wet. Both bottom corners on the door are partially gone, so I can't take exact measurements all the way, will have to extend a line from farther up and go from there. The doors are off the cab, and the cab floor is shot, (ok, just about gone) so it's no longer possible to check gaps all the way around.
I did buy all the parts needed to replace the floor some years back, they are on the shelf. But I see now they offer 1-piece floors and that seems like a better option, especially for a newbie, less chance to mess up something while putting it all together. But that's getting ahead of the game at this point.
Last problem is TIME - I have way more projects going than there are hours to do it in, to say nothing about energy in the old guy!
But I'm having fun, and learning, and I thank all of you for the helpful suggestions. When I can, I'll plunge in and start doing it, which is really the best way to put it to the test.