Well Keith, as you know, with a Custom build there's a bazillion things to think about. I wouldn't overthink this one though... you already know what you like, stick with it. You might even let the shop take some measurements from your favored Series bass neck profile when they're ready to whittle it down. But I can tell you from experience, when they did my Custom fretless, I asked for them to replicate the profile of my Classic taper Persuader 5-string into a fretless, and they absolutely nailed it. The only way I can tell them apart in a blind test is that the fingerboard edges are carved-under on the fretless, and squared-off on the older bass. It's just how they were made back then. There's a tactile difference between the finishes. That's it. The necks are otherwise identical.
I do know what you mean about those old Series bass necks though. I played a show right before Christmas with old 77-621. It's like that bass was just made to fit in my hand. If I were going to commission another new build, I would certainly model the neck after it.
Happy New Year... Looking forward to seeing your bass come together!