Butyl sound deadener on rusty floors

I recently pulled out the vinyl in my truck to replace it with carpet and there was a lot of rust and also holes.Cleaned it up with rust converter and JB weld steel stick epoxy putty. Seems ok now.there were some Waterleaks and i think I found them and patched them. So now i'm wondering if I should put some butyl type sound deadener down to seal the area from moisture.. On one hand I'm hoping it will keep moisture away from the previously rusty areas.But if that ever failed I would not be able to pull the sticky stuff back out. Then I would definitely have to replace the floors.
I love that truck and I want to keep it but it is definitely never going to be a show truck. I just want to keep it from slowly rusting away from under me. What should I do, Butyl or just leave it and put the carpet down over the painted floors?

Not in my truck, but on my Chrysler Lebaron convertible I used spray-on bed liner (the kind that hardens).

This is essentially what I did with my Bronco. Fixed water leaks, ground the rust away, put POR15 down and fiberglassed the couple of holes. Let all dry, painted and put sound deadening down.

May not be the professional way, but will last a long time.

Here is what I did:

https://forum.garysgaragemahal.com/1982-Bronco-351-4x4-Code-name-Esperanza-tp9221p139156.html

And painted:

Butyl rubber can be removed with paint thinner if you ever need to. Kilmat is one of the butyl sound deadener products I found to be among the cheapest but it's not advertised AS butyl (which is weird because it's superior to asphalt). For additional protection you can place desiccant packs throughout your cab, just not in direct contact with metal surfaces.

I'll look into the Kilmat deadener mats. If I put those mats down no moisture can get to the metal underneath , right? Except from the other side. I'l use CRC marine rust inhibitor for that.  I don't know what those packs are you mentioned.
The carpet I bought goes from the back to the front in one piece so it would be held in place by the seat bolts. I'm thinking about cutting the carpet into two pieces and use velcro to keep it from sliding. That way I can keep an eye on any moisture or rust issues without having to remove the seat bench every time.
besides I'm 67 it's not that the truck has to last another 40 years LOL

I used this from Amazon. It is a butyl and was very inexpensive.

https://noico.info

Don't forget a set of decent rollers as all of these need to be rolled to get good adhesion. When I decent, I mean metal roller with proper bearings. I had one with no bearings and it went in the trash..

Thank you, I'll do that.