As Paul referred,it's slim pickings out there for an authentic new 14"Bias-ply tire.Especially a 50 series..I did find a pair of older 14" 50's that were just too far gone and beat.Makes sense as I can't see anyone buying em 35 years ago not using them for what they intended.
Here's a good representation of what's on the 14" Bias repro market today.(15" incl. in here too)
http://www.summitracing.com/search?SortB...14%20bias%20ply