Okay guys, putting my car back together after many years including a roof swap. Don’t know what year the new roof is but its got the 75(?) up retractable belts. Bought some Morris Classic belts but have no idea what size bolts go into the roof for the retractor. Tried metric, standard… went through my bucket of bolts. the metric seems to thread in maybe an extra turn or two but they all get bound up. The nut that’s welded to the roof panel - is it some kind. Of lock nut?