[franken]

Using different size cables makes no sense since exactly the same current flows out of, and into the battery. You can use jumper cables to add capacity to the existing cables to see if it helps.
Using another solenoid is a bandaid rather than solving the actual problem.
Look for hot spots in the cables and connectors that show resistive spots. Make sure the - cable is connected directly to the block.
Saying the timing was changed but not saying what it was or what it is now doesn't provide much info. Did it crank better when hot w/ the distributor disconnected?