Good catch, that was supposed to be temporary, it came on the frame. I do have a more correct nutted bmx collar.
Re: stem, I had it set up for me with a longer syncros stem, still too small for me, just a little bit but enough.
I probably have enough vintage parts for that bike, but for some unknown reason I am hording them. I must have the worlds largest syncros stem inventory I think I have 8-10 in different sizes both traditional and ahead set style.
When I knew I couldn't keep it, I went in my bin of NOS take off parts. The bar is from my 2013 specialized epic comp, the stem is from my niner gravel bike, the seat I don't remember but its a new take off (nice seat btw).....I had an old xt drivetrain, but frankly the (brand new) low end shimano stuff works better than that beat up stuff. New chain, 8sp xtr cassette, rings are newer....ritchey headset and fc bb are fine....I didn't have any xt brakes, I should have put on the avid brakes I found in a bin (trek 8700 carbon from '90), I did use the levers and a pair of old xt thumbshifters.
Oh, the rear wheel is a campy (???) mtb wheel that takes a shimano cassette....I can't remember for the life of me where i got it & I"ve got to search the barn for the matching front... I have 8-10 MTB wheelsets out there from back in the day.....
I can't believe the junk (good stuff) I"ve saved in over four decades of riding....
thanks for the feedback