I really like that tt setup do you remember what ebay user you got them from? and about how much? thx!
If you search "Mustang twin turbo kit" in eBay Motors, a bunch will pop up right away. Some vendors sell a kit that comes with all kinds of crap for $1000 and others sell a more basic kit for a bit less. But, none of the vendors sell the kit with downpipes... you'll have to make/have those made.
Now some free, albeit unsolicited advice on this kit...
Pros: makes good power (like most turbo kits that are actually running), spools up quickly, looks kinda bitchin under the hood.
Cons: headers are a realy PIA to deal with (very tight clearance on a few bolts), routing your driver side downpipe will be tough and you may have to go with manual brakes (like I did), the intercooler that comes with the kit is useless and a big restriction (I went to an eBay special 32x12x3 and it works great), you'll have to relocate your battery, you have to get an aftermarket alternator bracket, the driver side header/downpipe interfere with the clutch cable (if you have a manual tranny) and dipstick, the passenger side header touches an a/c line (if you still have it).
If I had to do it over again, I'd buy the twin turbo headers from B&G and piece everything else together from the stuff on eBay, including the turbos.