You don't need to cover everything.
what stuff like dynomat does is stop the sheet metal drumming.
the knock off. band stuff works well
now on the plus side of doing things like the floorboards is if you got rid of all the rust and
painted it with good epoxy primer and a quality paint it will be very rust resistant.
if you have a heat coming through the fire wall better to use other things on the engine side
used it on my MG and it is much quieter
