I don't have a picture, but I have installed antennas in many of them. Drawing on a 30+ year old memory of when I was installing business radios and cellphones for a living....
You have a few inches in the very back, but that reduces rapidly as you go forward. It goes down to about 3/8" at the narrowest point, which is about 3/4 of the way from the back. Then it starts to open up again, but not as much as at the back.
When you drill the antenna hole at that 3/4 spot, because that's what the customer told you he wants, and then you find out there's not enough room for the antenna mount, and you have t tell the customer you need to drill where you wanted to in the first place, and he's got himself an extra hole in his roof, well, you sort of remember what you ran into. Yeah, that was the first mid-80s Chevy pickup I did, and the last time I drilled that far forward.
The customer is NOT always right!
By the way, there's tons of room to drop an antenna in the back, about 2" in front of the edge, and the coax will drop very nicely down the rear pillar, then can be run under the carpet to the front where the radio mounts under the ashtray. Well, for those who have carpet, anyway.....