Okay Allen, here's one other thing that you have to keep in mind... the strings as they go across the top of that bridge are arrayed in an arc, just like on your upright, so it is somewhat critical that the slots be cut the correct depth. Though the bridge height is adjustable independently from either side, if the A string or E string is cut too deeply into the saddle, it will bottom out before the other does. That will create a setup problem to say the least!
Just another observation, it doesn't look like the break angle is all that drastic over the saddles. This will make filing them easier but you will have to take care not to hit the bridge rails if you're going to file them while the saddles are mounted on the bridge. I probably don't need to tell you this but it would be much safer to mark where these slots are going and then clamp the saddle in a vise to file the slot. I might go as far as to rough them in while they were in place on the bass... (if Zelda was not watching) but that's it. That 1975 channel bridge is gonna' be tough to get an exact replacement for if you goof.
I have taken a couple pictures to illustrate how to measure the distance between the strings at the bridge with the dividers, and another to show how to hold the file when filing the saddle slots. Ideally, the slots should be about half the diameter of a string deep, and just a little bigger in diameter. When choosing a file, get the right size... I can't emphasize this enough. E-strings are typically something like .100 -.105, so I'd go just a fuzz bigger than your string.
Let me know if you need other pictures or more information, as always feel free to use that phone number or hit my private email. If you feel like you're getting in over your head, just stop. Can't go wrong there!
