Why did you not go with a front mounted, electric AC compressor? Aside from not having to route the lines the length of the car you’d have freed up the space where the compressor now is to mount the alternator. This would have made the bracket for the alternator much simpler and, with the smaller diameter pulley and no clutch, you’d have saved a significant amount of trimming on the chassis member.
The answer to this question is simple. I didn't even think about doing an electric AC compressor. Doooh! That probably would have been much simpler and a better way to go. I'll file that idea away in the memory bank and hopefully it will pop up next time I have a similar situation.
You mentioned that you figured out how to trim tempered glass with a bit of trial and error, but you didn’t mention how. I know that tempered glass has an edge zone where the glass is untempered, so a small amount of re-working should be possible but you mentioned ¾". That is a lot. Every piece of glass is different – was it just hit or miss in finding a window that allowed enough room in the tempering to achieve what you needed? I’d love to hear more. I have one project that has been on hold due to the same problem. And for me, ordering a new piece of glass would be expensive.
So making a piece of tempered glass a little bit smaller than it was. What Howard posted was techniques to cut laminated glass which is definitely different than tempered glass.
The first bit of wisdom I can pass along about messing with tempered glass is that when it decides to change form, it does so in an almost explosive way, so cautionary preparations are definitely needed. By changing form, I mean going from a single sheet of glass to a million much smaller bits of glass. This isn't the desired outcome but you need to be prepared just in case it goes there. What I've found to work best is to wrap the glass in a couple of layers of bubble wrap that's taped up for full containment. Only leave the very small part of the edge you plan to work on exposed. The bubble wrap also helps to eliminate pressure points against the glass that can introduce stresses on it.
What I've found as the best tool to "grind away" the tempered glass on the edge you need to make smaller is diamond knife sharpeners. The ones I use are the Dia-Sharp line from DMT. These are a continuous diamond surface embedded on heavy nickel-plated steel. They come in various "grits" from extra course to extra fine. I use water as a lubricant and straight back and forth motions on the glass edge.
If you look at a automobile door glass, you'll see it has a rounded edge. I try to keep that same rounded profile while "sanding away" on the edge. I use an extra course stone to start and medium to fine stones at regular intervals to "re-polish" the edge. I've found that to much with the course stone without re-smoothing the edge can lead to the glass imploding. I'd definitely recommend you practice on junk tempered glass to get a feel for what works and doesn't work. If you're like me, you'll likely lose a few pieces of glass before getting a technique down that works.
The last bit is that once the tempered glass removal is complete, polish the edge. I polish with an extra fine stone and then 2,000 grit or finer wet/dry sandpaper. You want all visible scratches removed from the edge. I'd also recommend the bubble wrap stay in place until the glass has gone through a couple of warming and cooling cycles. For example, place in a hot sun and cool overnight. If the glass makes it through that, it's likely stable enough to withstand the vibrations and bouncing it will get in a driven automobile.
Best of luck and I hope this works for others.