Mark, this one is definitely an original and is 5/8" OD tube with a wall thickness of 0.100".
On this one, the hole at the frame mount end is oval but possibly from being run loose at some stage? The hole centre to hole centre looks to be 9.75" as best I can tell.
The flattened sections are 1.5" from the rounded end to the line of the tool mark at the end of the flattened section.
The headbolt hole measures at .390" now and the frame mount .540" - the orginal headbolt end would be clearance for 3/8" and the frame mount clearance for 1/2". That end was possibly slightly oval as there are shallow slots pressed into one side of that flattened piece (about .060" apart) that look like they were intended to prevent this slipping once tightened.
I only have one original bracket can't be certain of the hole size/shape at this end I'm afraid - someone else may be able to provide clarity here.
In side profile the bar is straight with the flattened section at the cylinder head end bent up at 10 degrees.
Looking down on the bar it has a 5 degree bend 4.5" from the end of the flattened end of the cylinder head end and a ten degree bend of the flattened section at the frame mount end - one of the pictures on the link above shows this fairly well.
Sorry about the verbal description - I don't have any CAD available so this was the quickest way to respond - let me know if there is any other details I've missed.
Ray
