Bed to Cab distance? ANYONE? I need a measurement!

[74Chevy74]

Guys I took the plunge and I'm making my Long bed a short bed, well everything is going well, I cut out what I was supposed to I just want to know if someone could give me some measurements on the distance between the cab and bed. I think it may be the easiest to measure from under the back window as close to the side as possible, opposed to the bed side. Hope this makes sense, just want to double check this dimension before it's fully welded. Thanks!