FWIW I've had 25 Imperials, from 59 to 68. None were upgraded or modified other than stock in any way. I live in San Diego, California, where "normal" freeway speeds often approach 80 mph. Never had a problem on any of the many 100 plus mile trips I've made. Never went to disc brakes (except for those that came with them, 67-68) and never had a problem stopping. That said, I try to keep my cars in safe-to-drive condition: good tires, brakes, IN-SPEC drums, front end, shocks, fluids, etc. I've hopped in "just purchased" ones and driven anywhere from 1200 miles (trouble free-64 convert), to 300 (trouble-prone 66 convert where top blew off, tire exploded, no heater (30 degree weather), and I STILL made it home. These are VERY hardy cars that were overbuilt when new, and most have aged very well. Have fun and drive.