tire width under stock wheel wells

You guys put things together well. I would like to ask a similar question for a stock '70 Dart Swinger and a stock '69 Dart, both running 14" wheels. What could the largest rear wheel/tire fitment be if I managed to relocate the rear leafs (replace stock with super stock springs) utilizing a spring movement kit? No tubbing, rolling or cutting. I may not touch the '70 Dart though, it's a cherry little ol lady car w/less than 49k.

Thanks for the help.