Brian,
The question(s) you ask are too subjective for anyone else but you to answer! Yes, a '72 or '73 "T' can be built-up to a very nice level of performance in a project car ... as Jack Olsen and Jack McAllister have shown!
But whether to buy or build the 'project' is something only you can answer. Why don't you take a look at the following pages, and ask a few, somewhat less all-encompassing questions?
http://members.rennlist.com/jackolsen/Jalopy.html
http://www.cheaterswayside.com/911/gallery.asp?sort=0&userid=57
http://www.pelicanparts.com/MotorCity/hatari/finito.html
http://www.cheaterswayside.com/911/gallery.asp?sort=0&userid=162
Good luck!
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Warren Hall
1973 911S Targa
1992 Dodge Dakota 5.2 4X4 parts hauler