I am by no means an expert, but a few simple things.
1- Improve the coil springs up front, not sure on the rear leafs asside from getting new ones.
2-sway bars! I would thing a mustang piece would work, but I have a couple from 72-76 cars that could probably work. If all else fails, try to find an older junk yard, and see what's out there. Maybe some car would have something that you could adapt. 2 door Torino bars will bolt right up.
I picked up a bar off a f350 dualie for my 1979 4x4 f150, just had to get some new endlinks, and drill a couple holes on the frame.
3-TIRES and RIMS-if you are running factory 14"x6" rims and running skinny bias tires, time for an update.
You could stick a set of 15"x7" stock ford steel rims on there, do maybe a 225/60/15 tire, or even like what I did on my '72, run some 16" police steel wheels and run a 245/50/16 performance tire.
I don't know what rims and tires exactly work on your ride, but do some searching on the web, on ford sites.
Keep in mind, you could even bump up to a big diameter rim, but how much cash you want to spend. a 15" tire is gonna be alot cheaper and easier to get than a 18".
As far as lowering, contact a place like Eaton Springs, they can custom make your stuff, just need to have the specs for your car, like, engine, a/c or not, etc.
addco makes a rear sway bar for your car. Back when i first lowered mine and installed a rear sway bar it made a huge difference. My car already had the big sway bar on it up front. 15/16" or something. It was what came in the 428 equiped cars. My rear leafs were replaced with big block spec leafs, they are fairly stiff.
Mustang bars do work. I have one designed for the later mustangs (67-70) on my 68 montego. Same thing goes for nearly all front suspension pieces, they're all shared with the mustang and falcon platforms. So springs, control arms etc. are all the same for the front. the rear springs are longer on our cars though. hope this helps
Generally, You'll have a pair of brackets tha bolt on tot he rear axle, then the end links will probably use an exsisting hole on the frame or you might have to either drill a hole or weld a bracket on to bolt the endlink up.
If you got a kit, should have instructions, but otherwise pretty simple.
If you can get it a 1 1/8" front and 3/4" rear will make allot of difference. But use ploy bushing for less give. Build your own subframe connectors to try in the frame. Even put in BBF front coil springs and rear leafs. Shocks just control the springs, they don't help the support of the vehicle itself. Wider rims and tires with the right thread pattern also.
If you make the Shelby-style change in relocating the upper a-arms you will lower the roll center and improve the camber curve. Both will make the car push less: the camber curve improvement will keep more rubber on the pavement, since it will keep the tires from going into positive camber on roll; and the roll center change will in effect result in transfer of load to the rear tires. In addition, it will likely make it unnecessary to add a rear anti-roll bar, especially if you add a couple leaves to the rear springs.
This is described best by Mark Ortiz in text you will find at the link below. Lowering the roll center will also allow you to run heavier springs and anti-roll bars on the front end, which will help you put put power down coming off corners (it will not, however, help with drag racing).
In addition to the front suspension mods, consider adding an extra leaf and a half to the rear suspension with the half leaf going forward from the axle. The forward half leaf will help reduce spring wrap and wheel hop.
If you would like to lower the rear end, then do it by having a black smith reverse the spring eyes and/or de-arching the springs. Lowering blocks will increase likelihood of wheel hop on braking as well as acceleration. De-arching the springs also tends to reduce bump steer since the length of the spring between the axle and the forward attachment point of the spring will not be changing as much on compression.