Single Rail OverDrive. I had one in a '82 Mustang GT that I bought new. It's an internal shift, aluminum and look like a Toploader. When you bought this transmission, what was it advertised as or did you pick it up at salvage? Do you have any pictures of it? It sure sounds like a bastardized set up? A Toploader should install with virtually no issues.
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Doug Bender
1966 Fairlane 390/428CJ Heads, 4-Speed
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