Floatation/foam for tine boat?

My boat is a 1974 Smokercraft. After 47 years of mice periodically taking up residence under the bench seats of this boat, I'm pretty sure the total amount of floatation is nowhere near what it had when it left the factory. I have a couple questions:

1. What types/type of replacement foam are guys using? Links?
2. Does the foam available now have a greater level buoyancy than what was available in 1974?

The bench seat tops are wood and a couple need to be replaced. I figure if I have the tops off, I should repair other things while I can reach them.

Thanks!

2 lb closed cell expanding foam, Coast Guard approved.

Can be found on Amazon or eBay

Also Coast Guard Boat builders handbook has a lot of information on floatation.