Tires: factory original replacement tires, google search, replacement tires

Question
I have a 1974 Impala Sedan and I need tires. I would like to replace with factory original style tires, being it is in excellent condition and has only 54xxx miles on it, and I am slowly doing a complete factory restoration on it. The door sticker says HR 78-15 and it currently has 215-15 on it. My question is whats the difference between the these tires and what brand did they use from the factory? I'm on a few different forums and nobody came seem to answer this as well as all the sites I find on the internet all say something different.

Thanks in advance

Answer
Neil,


First, HR78-15 is an obsolete size - using an obsolete sizing system called "AlphaNumeric".  

A quick Google search didn't turn up anyone who sells them nowadays.  The problem is that there is no modern equivalent.  The closest you can get is a P225/75R15, but it is slightly wider (1/4").

Here's how I did this:

http://www.barrystiretech.com/vintagetireexchange.html

The difference in tire sizing?  I cover that as well here:

http://www.barrystiretech.com/tiresizing.html

The sources that I have do not list the original make and model of tire for your vehicle.