My '66 runs 13.95/100.3 at best and the unibody is totally stock. Sub frame connectors shouldn't cost much to buy and install ($200-300 US). 300 or so horses shouldn't really be too much of a problem for a stock unibody on a classic Stang. I think you should question your mechanic a little on that.
Rev
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'66 Coupe, 306, 300 HP, C-4, 13.97 e.t., 100.3 mph
1/4 mi.
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