You would need the wheels (any wheels) for the placement of the flares in terms of height and fore/aft placement to ensure the opening was centered and even all the way around.
Incorrect backspacing however would force unneeded modification to the flares to adjust the amount they stick out. This really applies to fibreglass and not metal because metal flares are completely modified anyway.
In my case and Laslo's, wheels with proper backspacing can now be ordered without modifying the flares or the need for spacers or longer studs.
I just spoke to someone who ordered wheels from Byers and his rear BS is roughly 6". Don said they would be "perfect".
My rear BS is 4.35". He will be installing Hall flares like mine.
You can imagine that he is pretty upset after finding out that he has to modify his flares or adjust otherwise. I have spoken to many in the same scenario.
Will
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