Here's my two cents.  I would say if you are going to go through the troubles of a swap, just start with a V8 car instead.  That way money spent will be to improve on the V8 instead of converting everything.  $5,000 will go a little farther on an I6 and with the lighter weight up front you can have an excellent handling car.  I may seem a little biased towards the sixes as my 66 has one, but I just think they are cool little engines that are often overlooked.  Like Mercury said, Clifford Perf. can really wake those engines up.  The choice is yours but I would say keep the six and dress it up.  You'll have a good paying job soon enough and you can just buy a cherry 289 Stang and have the best of both worlds 
BTW, before I started working on my I6 I didn't know that much about cars.  The six is a great way to get your feet wet and parts are very cheap!
Good luck
Brett
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66 Tahoe Turquoise Coupe
Laser Red 96GT Ragtop
30 Years & 30 inches apart in the driveway!