+1 on the congratulations! That is a desirable frame and the condition looks to be very good. I would encourage you to keep the Simplex dropout as it is. The Shimano Crane GS is another RD candidate for your situation: it uses the threads but has its own stop tab.
The original seatpost was nothing special - a straight chromed steel post - so I'd keep the Zeus seatpost.
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72+76 Super Course, 74 P-10+ 79 Tandem Paramounts, 84 Raleigh Alyeska, 84 Voyageur SP, 85 Miyata Sport 10 mixte and a queue
Last edited by Schreck83; 09-25-22 at 05:15 PM.
Reason: GS, not GT