Distributed power using point of use DC-to-DC switching supplies -- too bad these old Williams boards weren't designed like that to begin with. I wish the current capability was a bit higher as those could have been shoe horned into other places as well...
With the demise of the LM323K voltage regulator used in ton's of machines - little switchers such as these or the ones made by companies such as Texas Instruments look to be the answer. Pull out that old LM323K, install a highly efficient 5V, 5A regulator (able to drive LED displays in addition to CPU, etc) -- more current, less heat and a more reliable machine. I don't have the time to work on my LM323K drop in board (which also covers 2N6059 series pass transistors) but *maybe* somebody else here does ... hint, hint.