Last week my 83 240 B23F with 300K+ started to jerk or buck while driving pretty violently. The car finally cut off after about 10 miles of me trying to "drive and coast" home and I had to have it towed to the shop as it wouldn't restart. At the shop the next morning they started the car and it ran for about 10 minutes and cut out. Diagnosis - bad fuel pump. It was replaced along with the filter and both pump relays. Shop reported that the in tank pump sounded fine. Now the car is starting the same routine and will cut out after it warms up and I drive about five miles. It seems to idle fine for long periods of time, but cuts out under load or higher rpm. I replaced the engine and ignition harnesses about a year ago; when I had the manifold off I replaced all vacuum lines and I cleaned out the flame trap/box. AMM is about 10 years old, rotor, cap, plugs and wires and airfilter are all recent. Timing and advance was done a few years ago - (I "lost" my timing light and dwell meter LOL.) Likely causes at this point? Fuel regulator, Injectors, Catalyst, O2 sensor, or electrical ? Any diagnostic tips would be greatly appreciated.