Someone bought only an Altair CPU PCB and bought all of the parts to assemble it himself. He made a few interesting modifications. One of them was to remove a zener+resistor voltage regulator and replace it with a TO-220 style voltage regulator.
Another modification was to replace the 2 "one shot" clock generation circuits with an Intel 8224 (the correct/industry standard way of doing it, MITS was cheap). The 8224 circuit that he did is by far better than the MITS method. I haven't had any problems (that I am aware of) which were related to the clock circuit, but I would be very willing to try it. Maybe I can get him to explain the modification process here.