I have a 70's Grizzly it is one of the yellow and black riser. I have an SBD skinny string on it.
A lot of guys will tell you not to use a FF string on your bow, There are quite a few of us that don't buy into that, I have been shooting pretty much all of my Bear Bows with FF on them with no ill effects. I actually gained 9FPS on that particular bow and it is whisper quiet, I personally think that at 45#s you wont hurt that bow at all, that being said you make up your own mind on that. You will get the maximum performance out of that bow if you go with the FF string.