You could convert it to a 1" threadless headset and just have the steerer tube of the fork extended. Then you won't be limited by other things like total steerer tube length or having to find one of those old "7" style stems that are long enough to get the wedge below the top headset bearing.

It's not difficult for a welder to cut off the steerer tube a few inches above the fork and then using an inside union, braze a longer section of non-threaded tube onto it.

Of course it's going to require more parts, but they'll be easier to come by. The pista type stem will let you change bars easier or stem length easier with less hassle.

Seems a better topic for the mechanics section though. Maybe framebuilders.