Poor handling at speeds?

[Pont406]

Ok, it's 69c10 that I converted to 71-72 front disc brakes with stock parts. Stops better but due to low vacuum 12-14", hydroboost is on it's way soon. Now at high speed around 75-80mph and above steering is too sensitive. After making a fast lane change it will need a correction. Anything at 70 and below handles great. I think it will need a front sway bar, possible rebuilt steering gear box and recalibrated p/s pump. Right now pump is out 78 T/A. So, which repair will get me the most? Just trying to make this truck handle a little better before I hook a trailer to it. Thanks