I found Lazorjock`s long thread, and he mentions putting in the newer window`s. Looks like they go right in.
I`ll copy and past the info...
While I was waiting for the primer to dry, I got down one of the OBS quarter windows. There's not a lot of documentation on swapping them and I'll do a full write up once I'm done but here is a preview. The OBS window looks like this.
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The big difference is that the old style glass is sandwiched between the outer metal frame and the cab. The OBS window is a single piece unit. You can see it has studs sticking out the back.
And here's what it looks like installed.
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Yep it drops right in the hole.
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The studs sit just inside the opening. The washer nuts grab the inner lip of the cab metal and will tighten down pretty good. The reality is that you probably wouldn't have to make any modification at all. Just apply sealant and snug the nuts up. I'm sure the sealant is doing most of the work holding it in. I'll probably weld a few tabs in to make me feel better. Like I said, I'll do a tech with lots of pics once I finish it off.
If I come across any additional info, I copy it.
It`s a long build/project thread, 200 pages, only up to 38.
Goat