'Full load' K5's and trucks with manual tranny's were pretty rare. I'd guess that well over 90% of the optioned out truck got the auto tranny. Until I found mine I hadn't seen another loaded K5 with a manual tranny before. Of course nothing on my truck is orginal anymore so it doesn't really matter, and I don't have any plans to do a full-on concours resto either...
A few other rare combo's i know of are any of the K5's with 3 on the tree, and the few that got the A833 OD 4 speed. I know both exist but have never seen either one in person. I have seen one pick-up with the A833, but it was 2WD...
I've also never seen the factory soft top, although I've seen mention of them in the GM literature.
Rene