If it's a 58" bow that's shaped like a new model Grizzly, then it's a 1967 bow (the first character "7" in the serial number denotes 1967. I believe this dating method only applies to Bear bows made from 1965-1969). Bear made 56" Grizzlies for a couple of years, I think in late 60's or early 70's, but the vast majority of Grizzlies are 58". Older Grizzlies, up through 1963 I believe, are 62" long.
I agree with dbd870 that I wouldn't go over $150. Even it the bow is in excellent condition with no stress lines in the glass and a good finish, the drilled holes hurt the value somewhat. There are lots of Grizzlies out there, lots with drilled sight or quiver holes, but also lots of them without holes.