MT's in those sizes are quite common on 4.6 Cobras. I hear good things about the performance of MT's on the track, but like every street/slick hybrid, they wear down FAST. Be prepared to swap them out quick if you plan on daily driging them.
Also, I would suggest checking out Nitto 555r Drag radials in a 315. Depending on the sectional width of the rim you are looking to mount them on, they may work and would probably be less expensive than 305's.