Even the stock F250 steering is terrible in the 78 truck. That short drag link and push / pull design is horrible at best.
You will have to perform some interesting fram upgrades just to squeeze that 78/9 power steering box inside of the frame. The crossmember will make that an interesting venture. Your existing box is suitable, and the problem you have is with the inverted "Y" design, and not entirely with the steering system. Instead of this system you can and should go with the inverted "T" design, and call it good. This will be fine for the minimal lift that you intend to run.
Now, the suspension modification that you intend to install is reasonable, and will require some fabrication, and to me, it seems that you will not gain anything by throwing some front leafs up front. You are not changing the axle, and will still have a D44 up there, so other than running leafs, is not really gaining you much. Seems like it would be more reasonable to just replace the spring bucket, and be done. Much easier to run what you have, and the coil spring set-up is plenty strong.
You also intend to run a rear dana 60, and again, with a 30 spline rear axle, you once again will only gain a minimal amount of axle strength. This is mainly because of the difference in axle design, full float VS semi float, but in this case, the 9 incher can hold its own.
Save some money, and keep the wheels that you have and keep fabrication to a minimum by just fixing the parts that need to be fixed.

Mounting the shackle pivot correctly will be the toughest part of your intended modification, but again you are not gaining any strength, and this seems like bunch of time without a reward.