Series I 2+2 Automatic Transmission failing

A friend who is a British car mechanic told me my automatic transmission is failing. It has a 3.31 diff . So, what is the prevailing thought?

  1. rebuild
  2. convert to manual 4 speed (can this be done?)
  3. convert to manual 5 speed

I have looked into the Tremec 5 speed from Driven Man but I’m hearing they are not making the conversion kit any longer.

I would appreciate any thoughts on the best approach. Seems like going with a manual is my preference, but I’m unclear on where to turn.

Thanks in advance

Mark
San Rafael, CA
Series I OTS (67)
Series I 2+2 (67)