I'm still trying to get my spare tire stowed on my 1969.  As I understand it, stock was an F70-15.  My spare is a GR70-15.  Anyone care to hazard a guess on the difference in tire width?

Trying to decide if there is no way a GR70 will fit in the spare tire holder.

If I recall an 'F' or 'G' pertain to a LOAD VALUE. The 70 indicates an 8.6 inch  section width . Of course the R is a radial designation. That being said, I'd say GR70- should fit. 

You can lower the front of the tub far enough to get a wider tire/rim in the tub. I had to do it on the '74 to get the 225/70/15 in there where the original size was a GR70/15. It's kinda snug, but it fits, and doesn't bottom out.
The two front bolts/hangers for the tub go into the frame, and they have lock-nuts on them. Loosen off on the nuts, then you can back the hanger studs out of the frame quite a bit...the threaded part is fairly long. I think I ran mine out about 2 inches. Then tighten the lock-nuts back up. You'll also need to lengthen the rear hanger bolt the same way...just screw it out a little. It will only go so far, as there is a pin in the threads of it that will stop it before it comes all the way out of the nut. Once you get it screwed out, place the tire/rim in the tub, raise the tub, and latch the rear bolt into the slot on the tub bracket, then tighten the bolt back up as you normally would.
hth
I keep meaning to get some pics of how far down I lowered mine...I may do that tomorrow evening...

I got it installed.  The previous owner had moved the nut for the carrier bolt up into the frame.  I guess that was the only way he could tighten up an empty bucket.  Anyway, thanks all for the help and encouragement.

Doncha just love it when a plan comes together?
Glad ya got it stuffed in there...you'll feel safer now!

After all, AAA has to have something to replace the flat tire!

Yeah, that one's right! They'll only replace it if YOU have it!

Anothedr satisfied customer!!  Another warm fuzzy !!!