[Daves55Sedan]

If you watch old movies, you will notice '53 and later Lincoln Capri cars had much wider tires than the usual 4 inch wide tires all the Fords had all through the '50's. They may have been radials.
The factory 670X15's and 710x15's had 4 inch tread width had around 28 to 29 inch diameter respectively, resulting in a high side profile, unstable handling and overall lousy cornering.
In the '70's I ran G-78-15 bias ply tires on my '55 Ford. They had about a 5-1/4 inch tread width, but really not much better than the 710x15's but a little better at cornering.
I have P205-75R 15's on the front and P215-75R 15's on the back of this '55 Ford today and they are the best tires I've ever had on the car in over 40 years easily, not to mention they last ten times longer due to the much wider tread width. The downside is, they're hard to get on and off the back due to the lower fender well.
As far a tire pressure, forget the instruction sticker inside the glovebox door. Go by the stated tire pressure on the tire (usually in small embossed lettering up close to the rim). During hot weather months, run the tires on a couple pounds LOWER than the stated pressure, since hot air expands inside the tire and could result in overpressure and a blowout.
I think the perfect tire for these would be G-78-15 radials, but there isn't anything close to those dimension available.