What a great bike! My ‘83 Stumpy has the same SR Laprade fluted seatpost. I’d run with what you’ve got.
I too swapped out the solid axles for QR, a fairly simple job. The original wheel set was in good condition so I found a spare Araya 26x1.75 rim at the co-op to match and build into a dynamo hub so I can commute in the dark.
Despite the pretty serious wheel flop, it’s a really fun bike and actually handles front lowrider panniers quite well for bikepacking. It’s realy nice when a bike you have lusted after for so long lives up to your aspirations and you truly fall in love with it. I hope this one rides well for you!