Great ideas, as usualLooks like any one of your mock ups is a winner, based on the voting! Your stem is probably a 21.1, which is why your headset isn't working either. I wonder what shipping is to Sweden from Minnesota? I might have one that would work really well on your build. And a headset, the old Schwinn ones are smaller in diameter.
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This ^^^ !!! With maybe a smaller tank or metal piece that is suspended by the tabs, but with space around it so you 'see through' it, like your fork and the rest of the frame. Has a cool 'skeletal' look to it!
That’s really kind of you. Curious to see the stem you’re thinking of. Did Schwinn use 25x1.0 metric threading?