RockAuto sells FL820s for ~3.50, it's well worth it for the AD valve.
When someone tells me they have startup noise on a mod motor, I ask about the filter; if they won't fix that, it's not very important to them, so it's not really worth my time.
For restoring one back to new:
You replace the All the rubber (all bushings and associated ball joints/control arms/swaybar endlinks, front and rear)
The inner and outer tie rod ends
Shocks front and rear
New tires and a full 4 wheel alignment.
It will drive like a new car. I've done this a few times now.
After getting the Resto stuff done, there are some simple cheap upgrades:
PI swap, various degrees
PBR swap (easy as a brake pad change)
2002 GT inlet/maf upgrade
These are pretty cheap, and can be done from JY parts.
Something to consider is transmission updates; that seems to be my favorite thing to break.
There are tons more updates, but start with the resto work, and you'll be a lot happier.
Red '96 Cougar XR-7 240k mi. '02 4R70W, PST DS : '03 PI engine, 04 maf, 24lb injectors, 2.5" exhaust, '02 4r70w + Jmod, DirtyD0g TC + cooler + 3/8" lines, 255 walbro fp. Alpine system.
Black '96 Cougar XR-7 (Lazarus) 210k mi PI Intake, '02 4R70W, Jmod, PST DS, GrogTune, Konis, Mark LCA+Poly, racecougar Custom Engine Chain, and JL and racecougar Bracing.
Black '97 Tbird Limited Edition, '02 4R70W, 255 walbro, PST DS, PBR Brakes&SS lines, Toicko Blues & Springs, GrogTune.
"War Is Peace. Freedom Is Slavery. Ignorance Is Strength." - George Orwell.
Truth Isn't Truth. - Rudy Giuliani, 2018 Award winner, “Most Outrageous Diversion” by MSNBC for this quote