Find a later style GM dipstick tube that uses the improved lip seal.
Cut off the part that accepts the lip seal at the very end of the tube. Discard the rest of the tube, you only need the bottom end of it.
Carefully measure yours and cut it so it will end up same length as before, where it seals to the trans case. Cut and fit and have it welded up by someone who's not a hack. This is what I'll do with my TH400 tube and stick that I found fits my '64 Le Mans that never came with a TH400, the tube/stick assembly that works came from a '69 GP.
It's hard enough to maintain proper identification of all the tubes one might have in a parts collection. Having a variety of them properly identified, already modded and waiting for sale really isn't practical from a business standpoint.
Modding your own isn't that difficult and is practical because you already know it's made to fit your particular car and trans.
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1964 Tempest Coupe LS3/4L70E/3.42
1964 Le Mans Convertible 421 HO/TH350/3.08
2002 WS6 Convertible LS1/4L60E/3.23
1966 VW Type 2 Single Cab Pickup 140hp 2276
1956 VW Type 2 Panel Van 36hp 1200
1957 VW Type 1 Beetle 180hp 2276
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