Putting aftermarket necks on these I take it?

Nope. You don't need them. You have to modify the saddles to compensate them a little more than normal, use light baritone strings and set the action like you would on an acoustic setup for finger style. They intonate and play just fine.

So it's not a baritone scale. but a standard strat setup and intonated for B-B tuning.

Well, there is a little bit more to it than just the set up. Like I said I can only do these are with certain types of saddles and bridges. Normally you would be unable to compensate enough to get the instrument to play in tune.

Yeah. Tune-O-Matics kinda suck for tuning well below A440

There is also no way you could do this with a tunomatic. It's all in how far forward or back those saddles can go. I think if you did this with a tunomatic you would have to move the whole bridge back. The thought has crossed my mind to try though.

The other thing is that tunomatics tend to be on guitars with humbuckers and baritones genderally sound a bit better, or at least a bit more traditional, with single coils, and bright ones at that. The most common type of guitar to recieve full conversions, neck included, are fender telecasters. Teles are even twangier than strats with there narrow aperture neck pickup and and alnico 2-3 magnets. They sound baller as a bari though.

Low tuned teles are so much love. <3