I have 225/70 R15 Goodyear Eagle STs on my 1970.  I think they look great.  I like the big mean tire look and have had no problem with rubbing.  As far as handling I have nothing to compare it to as I got the car a year ago.  I need to replace them next year unfortunately.  I love the look but eagle st's are discontinued so am considering another Goodyear tire or Bf Goodrich radial TA's.

 Jim I have Grand Touring springs in the front and a new steel spring in the rear.

and how do you like it?

 It rides a little stiff but handles great. I put a rear sway bar on her last year cause she didn't have one, and that really hooked her up. I'm running 28 PSI in my tires now but I'm gonna try 25PSI that will make her ride better. The GT coils are a little thicker wire diameter than stock and eliminate like 98% of the body roll.

did it alter the ride height much?

 I belive it raise the car up about 1 in. I would have to check my records out the garage. After all it was the original springs since 73. My rear spring was flat before I put the new one in, now it has some arch.

The original size tires were F70-15.  

[QUOTE=jrflyboyVP2]I believe 225 70/15's are the OEM tire size equal to the old GR70/15 size.  [/QUOTE]

Do you have stock wheels or aftermarket? You may want to check the back spacing to see if they are letting the tire come to close to the frame when you turn. A deeper back space will bring the tire closer to the frame and visa versa with smaller back spacing. Check from the inside of the wheel to the mounting flange where the bolt pattern is. If it is deeper than stock (if you have other type wheels)then you may have tire rub.

I have the firestone 225-70's front and 255-70's in rear on stock 8 inch rims and no problems.