$350 or not nearly enough. For some reason people seem to think others will be impressed by the sound and speed. Also a '01 Mustang is NOT a muscle car or even a cool car for that matter. What is impressive is old beat up piles of junk that sit right, drive right, and are very quiet and smooth running.
Well to answer your question, about $400 to $1200 for a pair, depends on the brand and type etc. Now since you only want to do JUST a camshaft you will have to stick with a stage 1 cam. If you wanted to do stage 2 cams then you will need to upgrade your springs also. And finally if you wanted to do stage 3 cams springs are a must and a tune is a must as well. Then after which ever you choose you have to pay to have them installed and dont forget the gasket stuff and little odds and ends. I would say installed by a shop with you having all the parts it would total about $1500-$1800
A 2001 Mustang has a 4.6 liter modular V8 with a camshaft for each bank of cylinders, making a grand total of two camshafts. The sound your looking for is best generated by old fashioned old fashioned single cam overhead valve engines like the 5.0 V8 that was in Mustangs before 1996.
my opinion, Competition Cams!! i had one in my 351 cleveland, it sounded great, it was the largest before it would mess w/ power steering, A/C and other accessories, had a very nice loping sound to it!!