'67-'69 Barracuda rear tire size

Hi Larry
You will find the inner tire to spring is going to be the closest dimensions with the 8.25
I ran 7" 4.25BS Wheel Vintique Ralley with a 235/60/15 no rub. .75 to .5" tire to spring clearance.
P235/60R15 Section Width 9.5" on 7.0" Rim
P255/60R15 Section Width 10.2" on 7.5" Rim

Here's a BFG chart
http://www.teambuick.com/reference/wheels_tire_howto.php#chart

Mike