"Split the difference" and put a 165 TTSX Barnes in your old '06 and you're set for anything with hair this side of a brown bear (and in a pinch that would work as well, but were I goin especially for the big bears I'd want alot more frontal area and weight than any of the popular deer calibers!)
If your 308 just wont shoot 165/168s as well as 180s then I'd stick the 180 TTSX in it and never look back. Inside of 400yds you nor the animals are going to tell a tremendous difference between the 165 or the 180.
To answer your original question, yes you're splittin hairs 175 vs 180... No sense in trying to rework a wheel that's been in existence for over a century!