I'm assuming you want real glass because it won't scratch as easy?
We have the Honda flip up half windshield And it serves us well however I do believe it does scratch pretty easy...I try to be careful with it.
As for the slow vehicle sign yes the muffler cover is about the best place to mount it. Just make sure you get the proper clearance for the bed to dump without interfering with it... I had that problem at 1st and had to cut down the sign.
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