The new Holley billet metering blocks for the carburetor have still not arrived so I went ahead and re-did my battery to starter cables. I had originally used the IMI geared starter manufacturer's figure for current draw but I am pretty sure, in retrospect, that they were quoting the running current, not the initial surge current of spinning the crankshaft. I had calculated that a #6 AWG cable should be OK for a reasonable voltage drop and the engine did start OK but it was clear that the starter was starving for current. Yesterday I made cables from 1/0 AWG welding cable, soldering- on copper terminals on both ends. Rather than removing the #6 AWG positive battery cable to the starter, I left it in place and simply added the new cable in parallel. Instead of relying on the chassis to return current to the negative battery terminal, I made another heavy cable and connected it from the battery to a hole in the aluminum adapter plate from my SBC to G50. The cable is "welding cable", a very flexible multi-strand copper cable with a tough insulation cover.
Snaking the cable through the chassis with the bodywork still attached was a chore. The car was raised off the shop floor on jack stands so there was very little clearance under the car. I told my wife that had I not been an active caver in my younger days I would not have been able to do it.