Another opinion, which is worth what you're paying for it.
When you make your purchase, whatever that is, stick with the .45. Being the original design, the five-inch Govt. Model in .45 is the least likely format to give you issues. If it's just going to be a weekend range banger ammo cost shouldn't be a huge concern. Besides, since your chief interest seems to be historical I don't think you'd be satisfied with anything else.