Really you can't buy just a decent clutch "kit" for only $150. You can probably buy a cheapo clutch for that but it will likely live a very short life behind a supercharged engine.
Valve tap doesn't mean a bent rod, the two don't go together. (By the way, 4.6 OHC engine don't HAVE pushrods). If you can hear it at the top of the engine, you may have a valve spring/camshaft related problem. You just really are going to have somebody look at it and figure out what the noise is to get any sort of realistic estimate. If it is instead a connecting rod knocking down lower in the engine, the best way to go would be go shopping for a good used engine.
Here in SC, you can get a normal engine swapped for $400-$800 at independent shops. IF you need one. Most shops will charge a bit more than that because of tranferring over the supercharger stuff.
A complete clutch job including something like a Ford King Cobra clutch set will run you about $800. Around here. Lots of places are higher and the Ford dealer's price will likely scare you to death.
Lots of Mustang part places are online so you can price a clutch kit yourself. If you want a MotorSport clutch or something most transmission shops will order you one or don't mind if you buy it yourself.
You can go here-http://www.car-part.com/
to check out prices on good used engines in your area of the country.
Keep in mind the noise could just be something loose somewhere that needs tightening back up, you don't need another engine to fix that sort of thing.