Need Measurement from Serp Belt Car

[AMC of Houston]

Hi All:

My waggie has a serp belt banshee squeal from a belt alignment issue.  Problem is an aftermarket idler pulley (the one up high on the left side of the engine) that a PO put on the car that is too close to the engine.  Now that Crown is once again offering a correct pulley, I'd like to get one on the car.  However, the original spacer is also gone.  I can of course make a spacer; but I don't know how long it should be (the AMC Standard Parts Catalog doesn't list the particulars of that spacer).

So, can any of you folks with a serp belt car measure the length of your pulley spacer??  It should be out in the open for an easy measurement.

Thanks in advance to anyone who can assist!

[Canoe]

Probably easier for someone to know if theirs is a match to yours if they new the year, equipment (photo for confirm?) and standards (49-state, Cal, high-alt, etc.).

[AMC of Houston]

According to the Eagle parts manual, all the 6-cylinder serp belt cars used the same spacer in that spot.   I know I could just eyeball it and cut a spacer; but I'd like to know if my hack job was correct!