I bought a polyurethane suspension kit from PST including control arms, stiffer coil and leaf springs with insulators and the largest front and rear sway bars they had for my '69 standard. Unfortunately, you have to use your old outer shells from your original bushings. It definitely made the car safe to drive as braking (stock disc brakes) and handing improved, but I was not completely impressed with the sqeaky front coil springs that make the car sit up too high (351W) and the made-in-China looking control arms.
I had previously heavily modified the front and rear suspension on my daily driver 1970 LTD also and bought the large front and rear sway bars, and the polyureathane bushings from PST, and plated the bottoms of my stock upper and lower control arms, as well as my rear trailing arms. I had custom front and rear springs made up, and used Moog suspension components, Billstein shocks, 17 inch custom steel rims, and put air bags in the rear coils and the results are astounding. This car with the stock front disc brakes will not lock-up and fishtail all over the place when you slam on the brakes and has surprised many a driver on the road with it's handling. The front end will also not excessively lift when you exceed 100. I would say go with polyurethane if it's a daily driver, but I would only buy the bushings from PST and get better quality control arms/ball joints somewhere else.
JAMES