Drop spindles + 15" wheels

[shifty]

Quickie, since nobody in the 67-72 forum was able to really answer -

I've heard of clearance issues on certain brands of spindles while running 15" wheels, and the spindles had to be ground down to work. Someone in another thread suggested that this is just a matter of geometry, and can't be avoided. I'm not sure what to think.

I figure if anyone knows, you guys would.

If it is a matter of geometry, is there a certain amount of drop that will absolutely result in rubbing and, thus, grinding parts of the spindle down? Like, maybe 2" won't rub, but 2.5" will?

If any of you 73-87 guys have bagged your trucks with dropped spindles and wheels that are 15" or maybe 16", what brand of spindle did you use, and how many inches were they dropped?