I recommend Stan and Denise at SDJ motorsports in North Carolina. They built my partners EP 12A and he won the S.E. Div regionals in it. We ran this past weekend at VIR in the ECR and his engines finished 1-4 in the first race, and for sure 1 and 2 in the second (didn't look a the 3rd place finisher). They roam the S.E. races and provide excellent tech support. Stan has developed, and is in the process of developing more custom 12A race parts (Air-filter setup, Header, suspension parts). I can dig their number up if you'd like it. They are EXTREMELY reasonable, and very easy to work with.
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Balz
#67 IT-7
The only John Deer green one going!