Following up......
For those of you that are interested, I thought I'd let you know how things worked out.
I did exchange a couple more emails with Jay at GF, and we were cordial. I think Jay, in our first emails, may have missed the fact that I was inquiring about an old-ish Gibson rather than a kit guitar or cheap import. Anyhow, in his last email he explained that GF's target market for its hardware is for inexpensive Asian import guitars, and that if he had a vintage Gibson he would be looking for a Tonepros, or period-correct hardware off Ebay.
Enough said - I'm satisfied with his response and that's the end of it.
Now to the guitar. I did sent back the GF bridge that didn't fit. I received the StewMac bridge on Saturday and installed it.
First I reinstalled the orginal bushing that I had removed (after first verifying that the stud threads were correct), and made sure the other bushing was seated properly. The StewMac bridge wasn't a perfect fit, either - the stud spacing was ever so slightly too narrow. Fortunately I still have the original bridge studs, which are slighly narrower where the bridge fits, and this allowed the StewMac bridge to slip on.
The intonation is not perfect. The adjustment screws are not quite long enough, so the fretted notes at the 12th fret are slightly sharp across the board, but I could at least get them consistent from string to string. Regardless it's pretty close, and on playing it works just fine. I was able to set the string height correctly and so the action is still very good. The neck on this guitar is very fast, so it's lots of fun.
As for the tone - until I started learning stuff on this forum from Muttley and Light and others, I would not have thought that different bridges could have much of an effect on an electic guitar's tone. I felt instinctively (for what that's worth

) that a big brass bridge like the one I removed would increase sustain but that's about as far as my thinking went. This smaller, lighter bridge has really brightened the tone of the guitar - it has reduced the muddiness of the neck pickup and helped a lot of midrange come through. And I'm not noticing any adverse effect on sustain - the guitar still sings nicely.
notCardio, I'm sure you will approve of it's closer-to-original appearance, bridge humbucker notwithstanding.
Anyhow it all worked out in the end so Zaphod is a happy camper.
