John,
I would suggest that you should first check whether each leg of your forks is straight (at this stage dont worry if the two legs are twisted). Then check whether the steering head stem is straight (an easy way to do this is:- obtain a piece of steel tube with a bore the same as the internal diameter of the botom steering head bearing, get the end machined true - this can now be slid over the stem and with it pressed against either the bottom bearing or the bearing seat, the top should be concentric with the stem). If these checks prove the legs and stem to be straight, then the damage is in the bottom yoke. The next task is to get the tops of the legs and the stem in the correct alignment using a new/good top bridge plate as a gauge. Small amounts of adjustment may be possible with the forks cold, but any major tweaking will require the yoke to be heated between the legs and the stem to prevent fracturing - only heat to a just perseptible dull red and dont allow any brazed joints to become overheated. When you have finished, the bridge plate should fit without having to spring the legs and the two legs should have no twist in them (check by laying the forks on a flat surface).
With this done, your machine should handle buch better.
Good luck with the repairs,
Eddie.