I have the 48 myself and have been renovating it for the most part I know you might not want to do that but even with the larger safe your looking at now you can get much more room out of it using things like rifle rods and making your own shelving to fit your needs. If you have time or are intrested check out fubarprotocal on youtube.
These are a couple of his vids he might have some more that goes in more detail on his channel.
I have a 48 wish I would have gotten a 64. I bought mine from circle A hardware in albany. If your willing to drive and haul yourself you will save hundreds. He advertises on la sporstman
It's really nice I got it for a steal from the old academy in Kenner, although I don't have but 10 guns including pistols I can't see me needing another safe. For those that still need more room though I would strongly suggest viewing those links.
The pistol rack I did was really easy to do not to mention it just looks so much cleaner than some of the racks available that take up needed flat space in the safe.
Fire rating mainly depends on where you live. If you are out in the bayou then you should look into something higher, but if you are in town i cant expect a house fire response time would be more than 15min.