I have a white lower unit with a long shift shaft, and I think it has the (long) driveshaft too. The seller I bought it from listed it as a "5.5 hp, 50’s/60’s Johnson". If you don’t have luck anywhere else, let me know, and I’ll tear mine apart. Please double check to be sure that every year takes the same part number.
(Frank is right about it being a unique, extra long shift rod.)
Sure, the 5" longer connector does replace that one. But the 5.5 & 7.5 don’t use a shift rod connector. That’s why you have to pull the powerhead to disconnect the shift rod.
BTW, although it doesn’t apply here, for anyone that does use a 5" longer connector, it will work much better if you saw a slot near the bolt holes at each end, mimicing the slot in the short one. That will allow it to clamp down on the rod better.