Suspension
In the case of your truck (and all F100's pre-1965) you sport an I-beam straight axle. Although bulletproof and the very definition of "built Ford tough," its not exactly an easy front end to lower.
The question is: 1) How much money do you want to put into it? 2) How much fabrication skills do you have?
I'm going to assume that you want to keep the straight axle for the meantime. Without seeing it, I'm a little worried about the way the previous owner flipped the front axle over the leaf springs. Done improperly, it is potentially very unsafe. The first thing I would do, if the axle is still in relatively stock condition, is to get it back under the leaf springs. I hope the previous owner didn't take out any leafs too!
One leaf spring (being the main leaf) in the rear is NOT going to cut it. I'm sure you know that. What I would do is get a new set of springs for the rear, just to get it back up a little to be safe for now. I understand you like the way the truck sits now, and a rear axle flip (again, done properly) on top of a set of good springs would be much better than what's currently setup.
You can go ALL KINDS of different ways to lower these trucks, from mild to wild, and everything in between. Depending on how much money you have, you could swap that straight axle out for independent front suspension. This can involve some serious fab work, and all the possibilities going down that route is another huge conversation. Others will suggest getting your stock axle dropped up to 3". And there's always monoleafs, de-arched leaf springs, proper axle flips, etc...
So anyways, these are just some quick thoughts of mine. Kinda random and jumbled, but I think it'll be of some help.
Why don't you let us know what you want to do with the truck and maybe take some pictures and post them here. What are your plans? How far do you want to take this project? Are you new to this?
I wouldn't drive the truck the way its configured now. Just my .02 cents. Good luck; there's tons of info on these boards, ask any questions you have! Later --Matt
Here is my rear suspension. Slightly custom four link with upper adjustable links to set pinion angle and Koni adjustable coil overs in the straight up position.

Here is my front suspension. A Dakota kit from Industrial Chassis. Uses common 86 to 96 Dodge Dakota arms spindles and calipers. you can also select between bolt patterns 5 on 4.5 or 5 on 5.5 by adding full size rotors. calipers and bracket from a 86 to 88 D100/D150 donor.

With your suspension on the blocks persae it will crack the frame rails. Typically if you flip the axle relief is needed in the frame for axle travel. This can be the case for either front or rear. It sounds like too many leafs are removed and the suspension needs to be balanced out....Some times you can have the cake but it needs to be engineered in.
Garbz




