I'd go to the World Ford Challenge to see the biggest event. It's May 17-20 in St Louis.
www.worldfordchallenge.com
Other than that, any of the Fun Ford or NMRA races are very good.
If you do want to come to Canada, we have some good racing up here too. (as 88COBRA mentioned)
J&P are holding their race at Cayuga (near Toronto) this year on Aug 18-19. Lots of Mustangs & other makes.
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91 coupe
3.73's,long tubes,2 1/2" exh,ported stock t-body,ProM-77mm
cobra intake,edelbrock heads,B303,1.72 rr's
36lb inj's,tremec, & a Paxton NOVI 2000!!!
11.020 @128.95 on BFG Drag Radials (275/60/15)