More Steering

Now what I need to decide is how to mount the steering mechanism. Options:

1. The easy way, relatively speaking, is to cut out the steering system from the old bike and affix it under the seat. Unfortunately, the old bike's head is longer than the space where it needs to go, so this is out.
2. I could cut off the top of the old bike's head. This would allow me a solid steel cylinder to put the yoke into, and a system of bearings to make it turn easily. I would need to devise my own way to keep the yoke from pulling up out of the head, and I would lose some of the anti-wobble effect of the longer head. Not sure the impact of losing the bottom system of bearings, beyond these two. Also, the yoke is too long for the space, and would also have to be shortened.
3. A variation of # 2: I could cut out the middle of the head, and attach top and bottom together. Would give me the bottom bearings, but would make the head a weak-point. All I could do to join them would be to apply epoxy, and this might also compromise the free turn of the handlebars.
4. Find a smaller head. The main problem here is the hassle and cost.
5. I could attach the handlebars to a perpendicular pole, then put a simple pin through the pole, and be done with it. Say, use a short bolt, one of those quarter-inch ones that has a length without threads. There'd be more wobble than either of the above, and it wouldn't have the bearings to turn so nicely around, so precision, high-performance steering is out. But it's by far the simplest.