Generally speaking, 3-nub, pre-71 6 lug wheels do not clear caliper retrofits. The inside profile of the wheel is different on 71 and up K5/10 wheels (i.e. 4 nub, 6 lug, designed for factory disk brakes). You can get the stock look that you seek with 71+ K5/10 wheels, but they are getting a little harder to find.
As for grinding the caliper - well, you can, that is an option. Much debate on here as to whether or not it's a good option.
http://67-72chevytrucks.com/vboard/s...d.php?t=327646
http://67-72chevytrucks.com/vboard/s...d.php?t=611451
http://67-72chevytrucks.com/vboard/s...d.php?t=615474