Unless you prefer retaining the original appearance, I would frame and plate, then cut holes for standard stand-still house windows.
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2003, we did this for our ExpeditionVehicle build.
I sealed with Vulcum 116 adhesive.
Over two decades full-time live-aboard:
1 -- the windows are in excellent condition
2 -- the Vulcum 116 remains soft and pliable.
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Cool truck!
We hear good things about them.
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[edited to add]
This might give you some ideas, our introduction with plenty of portraits, plus our reasons for our decisions:
https://vanlivingforum.com/threads/e...8/#post-576110