What is the backspacing of those 7-inch rims? Unless you already have the rims, 6-inch-wide rims will work fine for 215/75R15 tires. I temporarily mounted throw-away 215/70R15 tires on my OEM 5-inch steel wheels, just so I would have tires and wheels on the car during restoration, but 5-inch wheels are a bit narrow for 215 tires.  

Sir,

       Thank you for your input.  I think I am going to try 7" rims with 215/75/15 rims on my 1955 Ford Crown Vic.  If it ends up that I can't use my fender skirts it won't be the end of the world. I will keep you posted on how things work out.

Thanks, 
Ray

You're welcome Ray. 

Even with 205/75R tires on 15 x 5 Coker wire wheels, my dad was having problems with the knock-offs making contact with the skirts. He tried 2 different sets of skirts (OEM & reproduction), but it didn't help. However, the springs were original to the car and worn out. Someone had added an extra leaf to compensate plus Traction Master under-ride traction bars (I assume to control lateral movement of the rear axle assembly). The suspension is all new, now, I got rid of the spoke wheels, don't intend to run skirts, and in addition to the OEM 15 x 5 steel wheels, I have 15 x 7 alloy wheels/w 3.875 backspacing and 215/70R15 tires. Even without skirts, there was Little clearance left between the rear-wheel openings and the 215/70 tires. I ended up having the new rear springs re-arched to provide an additional 1 1/2-inches of clearance. In the front, I have Aerostar springs, 1 1/2-inch Granada drop spindles, and Wilwood Dynalite disc brakes. Unlike the results that installing Aerostar springs on full-size cars, I saw very little change in ride height when installing the Aerostar springs on my 55 Tbird; however, combined with the Drop spindles, I think I've got the stance I want/w no clearance issues. 

Thank you sir I appreciate your response.

Ray

Although I own a 55 Tbird, the OEM wheel & tire sizes were the same for both vehicles. If you intend to install skirts, I recommend that you stick with the OEM 15 x 5 rims and 205/75R15 tires. More than likely, you'll run into problems with the skirts if you go with anything taller or wider. Also make sure that your springs, bushings, and shocks are up to snuff. It makes no sense to replace wheels & tires and install skirts, if your suspension is worn out. 

    I own a 1955 Ford Crown Victoria and occasion have asked you a question.   It is time for me to replace tires on my car.   1.  Could you please tell me in your opinion what is the best tire brand to put on a Vic?  
2. What about .tire size considering  for looks and performance.
3.. I am going to be replacing rims also so what are your preference on rim size?  15", 16" or 17 rims.  Also on the rims what sort of backplace should I get so I am not
 hitting the fender skirts?