Thanks in advance!! I m upgrading from original 13" steel wheels to 14" steel wheels how big of 14" tire can I install without clearance issues has anyone else done this? Is a 67' valiant underneath the same as a 71' duster? thank You

Had a freakish rare 67 commando valiant here a few years ago, and near as I can recall, the front clearance is same as dusters and rear was a little tighter-not as generous as duster, demon wheelwells. Still maybe a hair more clearance than darts in rear wells.

'67-'76 A bodies share most of the undercarriage architecture. Your car may have more room than a Dart in some areas but the lower front corner of every wheel well is usually the limiting factor for tire height/OD.
Biggest setup I could get on a '73 Dart I had was 225/70R15 on 15x7s; never messed with 14s, so all I can guess is that a 225/70R14 on a 14x7 would be about it. BS should be 4.25-4.50. Check the fronts with wheels turned, bouncing car downward.
Hopefully someone can be more accurate/helpful than I am about 14s.