Need correct tire size for new rims

I lucked into a new set of Coker baby moons size 14x7 What would be the right size tires to put on it. I think the PO put in I'm guessing undersized tires and rims , because my speedometer seem to be off. It is reading slower than I am actually going. Next up is a complete suspension rebuild.

A 205/70 would be a safe bet I think. What is the offset and or backspace of the rims? You could probably go with 215/65 as well, that's similar to the wheel size bugman put on the front of his van, only .2" taller.

Thanks Seth.They have a 4 off set. I was wondering what tire size would match the stock tire size. My speedo is reading the wrong speed, and was hoping to get it reading right by getting a tire that will match the stock tire. Or does that not effect the speedo?

Just some info for you guys. Last night, I measured the old spare that came with my '64. Its 24" tall, off the rim. I'm thinking that we should probably have an overall diameter of around 24" for our speedometers to work "accurately"..

If it's way off you'll need to change the little plastic gear at the end of the cable in the transmission. Mine is fairly accurate and I've got 25"+ wheels.

This is a great on-line calculator, assuming a 24" stock tire size.  Once you get your 'effective' ratio hammered out, you can order a speedo drive gear that is closest to what you end up with...

Click here for the Diff Ratio Based on Tire Size

And this tire gets you a 26" tall tire.  Bringing a 4.00:1 Diff down to 3.69:1.

----> 205/75/14