Bicycle Mechanics - Stem adapter in place of locknut?

I've acquired a nice chromed straight-blade fork with a 1-inch threaded steerer. I planned to use it on my Wheeler Chiostra of early 90's vintage. The steerer, though, is a few threads too short for me to get good purchase on it with the locknut of the existing Shimano 105 cartridge-bearing headset. With the headset adjusted and a keyed washer in place, the end of the steerer sits flush with the top of the washer.

Normal advice, I know, woulld be to get a headset with less stack height. But at 37.5mm, the 105 is already one of the shortest I'm aware of. I'm wondering whether I could use a threaded-to-threadless stem adapater (photo below) that would sit down on the keyed washer and serve essentially the same purpose as the top locknut on a threaded headset. Obviously, I'd also have to use an ugly threadless stem, but I already have a couple of those in my parts box.

http://images.channeladvisor.com/Sell/SSProfiles/42000175/Thumbs/42/tn3_532921.jpg
Alternatively, does anyone know a good headset with stack height much shorter than 37.5mm? The only one I've found so far is the Tange Passage that Jenson USA sells for about $9. I'm not eager to replace the headset in the first place - though I can imagine that the sight of a threadless stem on my Wheeler might give me incentive - and I'm a bit leery of replacing it with something that might soon need to be replaced again.

I wouldn't use that threadless adapter to keep headset in place. Bite the bullet and either buy that headset or get a longer fork. Painful - but you'll feel better in the long run.

I strongly suspect you're right. But just so there's no confusion, the top theaded cap of the headset threads on and tightens down just fine. This would just be to apply the extra downward tension that a locknut usually supplies. So I guess one question would be whether tightening a qull bolt actually pulls the qull in the direction of the fork crown, or just applies force perpendicular to the steering axis.

A longer steerer is not an attractive option, since the search for this fork took several years. I'm currently running one of those Tange headsets on my commuter, and it's held up surprisingly well. So maybe that's my only real option. I just hate not being able to use the cartridge-bearing setup.

In that case yes. I'm running the same adapter on my bike now, I think it would be normal to assume that you if you can't wiggle the handelbars perpendicular to the steering column it also won't come up and out easily (I just tested this on my bike).

Maybe someone with a theoretical knowledge can chime on this anecdotal evidence.

The locknut stops the race turning and going out of adjustment. Small downward pressure wouldnt do the job. Try loktite, and give it time to set before you ride. Do plenty of riding close to home to see how it works before you go on any long rides.

try a headset with a smaller stack height

What if you had the top of the steering tube faced a bit more?

With a shorter overall tube the steerer would protrude further and you'd have more exposed thread, right?