need stock front wheel back spacing on 68 gts??15x6s/7s up front?? or 14"

yea i know all about the tire choices 14s are almost gone

just wasint sure if there is a benefit of spending the 250$ for two 15" wheels when i have nice 14s im running 15s in rear just breaks are my biggest concern going to disks and dont want to spend money to have 14s painted then end up needing 15s

I've got the SSBC disc brake kit on the front of my '71 Dart GT. I am running 14 X 5 1/2" small bolt pattern rallyes on all four corners. No interference anywhere.
What disc brakes are thinking?