In March we brought you the "how to" on making a trans tunnel large enough for an overdrive automatic transmission. The operation was carried out on a '67 Tempest convertible, which is significant because it's just one of millions of '64-72 GM A-bodies out there, and virtually none of them have overdrive. The problem is that wider overdrive transmissions like the 4L60E won't fit in the confines designed for a small Powerglide or Turbo 350.
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