I have converted a number of cars... 10 or 15 or more. I actually got my EPA license for R12 and then decided it wasn't worth the hassle and just started converting.
As John mentioned, you should replace the receiver/dryer and replace all rubber hoses with R134a-rated barrier hose. You should also replace old rubber or HNBR O-rings with Viton O-rings. But, it's all should and probably not have to. If you skip the hoses and O-rings you will probably end up with slow leaks. If you skip the receiver you will probably end up with reduced performance. I would *at least* do the receiver.
The only thing you must do is replace the high and low side fittings with the correct R134a fittings, or use adapters.
Make sure you use the correct oil in the correct amount!
You might look around and see if a newer Ford with a similar engine has a newer model compressor you can bolt in. If so, you may end up with a better performing system that lasts longer. Maybe. Sometimes newer compressors are more efficient and/or cheaper. It's worth a look IMHO.
To properly convert the car, you need to vacuum out the system then refill oil and R134a. Since it's a conversion you will fill based on pressure and not weight, so you need a set of manifold gauges and a thermometer to measure ambient and vent temps. You can buy that stuff for $100-$150. Depending on your area, it may just be cheaper to have someone do the work than gear up for one effort.