On a typical structural drawing, "HS bolt" would refer to ASTM A325 bolts. I would expect that A490's would be specifically called out as such because of their particular fatigue requirements.
As mentioned in the other post, the AISC Steel Construction Manual, 9th edition, would have allowable stresses and loading values for A325 bolts. However, the values depend on the loading configuration and the connection type, so you may want to get some more information from the structural engineer who designed the connection. If it's designated as part of a 'slip critical' connection, don't mess with it. Leave it alone.
In the typical case, you could make some assumptions that would give you a lower boundary to check against: bearing type connection, loads applied in single shear, and bolt threads included in the shear plane. That is usually designated simply A325, or if it is spec'd, it will read A325-N on the structural drawings. For example, a 5/8" A325-N in single shear specs out at as 6800 lbs allowable.
Good luck, and get more info as needed. Make sure all expected loadings and building code required loadings are accounted for.