If you have a 1000LB safe and its going to be on a wood frame foundation/floor you need to re-inforce the structure. Most houses are designed for 125 SQFT. This would be 12" on center 2' x 12".
At a minimum you need to be more concerned where the floor joists tie into the foundation plate/footing. Triple up on the 2x6 if you have that size or double up on 2x12 f you have that, what ever you have as main foundation floor supports needs to be considered.
Ensure you take the additional floor supports to the foundations plate/footing on both sides. 1000lbs is allot to place on an existing wood framed floor with a crawl space. If it were concrete I would not worry about it.
Let me know what size floor joist you have and the lengths (footing to footing) and I will be happy to give you the requirements to support that kind of weight.