I've never heard of the brand before honestly and I've been messing with these cars for awhile. $380 for an aluminum flywheel and a good clutch is a good price... but you are a 2000 so you have an 8 bolt flywheel which is the less common type of setup. If this flywheel he has has 6 bolts you can't use it. 1999 and 2000 model year GTs had the 8 bolt flywheels as well as all the Cobras and Manual transmission Mach1s.
What I did with my setup which was a 1999 engine... I found a brand new Coyote flywheel which is an 8 bolt unit and works with the 4.6L motors for $125 shipped on an online forum. You can find them usually for $100 plus shipping. Only thing you have to do is take a punch and knock out the Coyote dowel pins, tap in a $15 set of 4.6L dowel pins and good to go. The Exedy 11" Mach 400 clutch was $239 with a forum discount so I paid about $380 for that setup and it worked great.
That's another thing, always upgrade to an 11" setup unless you have a specific need for a smaller flywheel/clutch like a fast revving autox/road race car. You don't need that for a street car though and a heavier flywheel actually helps keep the RPMs up on the street in a bolt on car.
edit: You also have to look at what materials and everything this "Stage 3" clutch is made out of. "Stage" is just a marketing gimmick and it means precisely nothing as it is not any sort of universal measurement throughout the brands. One brand's "stage 1" could be way better than another's "stage 2", it all depends. I like the Exedy 400s because they are an OEM manufacturer, they engage real smooth, pedal feel is light and the 11" Mach 400 is rated for 500ft lbs at the flywheel. You will never get to that power level reliably on a 4.6L without a built motor anyway.
Also, for your power level if you don't plan on putting a supercharger or nitrous
on it anytime soon, you can just get a $125 Luk Gold replacement clutch and resurface the flywheel you have in the car now for $60 and be totally fine. OEM TOB/Pilot will be another $50 or so. You'd be into it for like $225 total in parts if that's all you need. Labor is always the killer on clutch changes anyway since the trans has to come out, that's why I always DIY.