What size battery ?

If it is an original car and you want to keep it that way I'd look up with Group Size battery it came with originally. Find the battery with the highest CCA's that fits your budget in that group size.

If originality isn't a concern and you aren't too constrained by what fits the battery tray then as a point of reference I've been driving my 170 Valiant with a Group 35 that has 550 CCA, but bare in mind that I'm on the lower Left Coast where "cold" is 30's F.