slant 6 question

Lou Madsen ("Dart 270" on the /6.org site, IDK if he comes here) somehow adapted a GM automatic OD (I think it was a 200R4) to a slant 6.
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Lou did use the 200R4 in his Dart. Car can run mid 12's in the 1/4 mile, and gets mid 20's mpg on the road. However it was not a inexpensive conversion.