A little summer rehab-suspension and seat questions

[Ace23]

I have car #1867 that was produced in 2004 and it now has 13k miles on it. Over the summer we are going to pull the motor to dress it up and change the cam. The other 2 things I want to focus on are having the seats repadded amd getting the suspension improved. I'm very happy with the car and this is this the journey I am taking getting the car exactly as I want it.

1. The driver seat is like a John boat cushion. I currently weigh 215lb but the previous owner was probably in the neighborhood of 270-290lb. What is the recommended practice for having the seats freshened up? Do I just need to take them to a local upholsterer or do I need to source some OEM padding from SPF? I pulled the driver seat bottom loose in the rear over a year ago so it won't hurt to get that reattached while I'm at it.

2. The car has 17" PSE Wheels and Goodyear eagle F1's that were installed in 2010. It rides okay until you hit the slightest rough spot or bump and then it will jar your teeth out. Can this be contributed to the shocks or is it more directed at the 17" tires? The other issue I am experiencing is the rebound in the rear is like a Cadillac.....when you hit a good dip on the interstate it has a slow trampoline style bounce and will literally pitch you up out of the seat. We did notice the previous owner has the rear sitting too low and it need to be raised 1/2" or so. Before I haul off and start looking into shocks I wanted to better understand what I am experiencing....maybe just a shock rebuild would do it. I have only driven one other car and it had 15" wheels and Avons and road twice as good....I'm sure much of this can be contributed to wheels size but I can't imagine many people running 17-18" wheels if it was this rough all the time.