2.5" drop spindles w/stock wheels question

[NC67Chev]

I'm looking for some information before I start this next project on my '67. My goal is to be able to run my original hubcaps after I put power front disc brakes with 2.5" drop spindles on my truck. I've found some nice original wheels (since my drum wheels obviously won't work on the front) that will allow me to use the hubcaps, but I've read that there might be some interference with the lower control arm on 15" wheels. Is it the 15" wheels that are the problem? Or, is it more related to backspacing? Or, is a combination? Can somebody point me in the right direction? Since I'm probably going to stick with 6 lug, I'll likely buy a complete set-up from one of the vendors. If I can figure out the exact tolerances (both wheel size and/or backspacing), I might be able to get some wheels from Rally America, Stockton, etc. that might rectify this.

Thanks everybody!