During the work replacing the blower motor did you happen across a system name for the whole system ; Evans and Denso are the most common.
Resistor block is usually just down steam of the blower motor in the spot where it gets max air flow for cooling, mine is within inches of the squirrel cage. Picture below. Just past the fan motor with all the wires.
Have you tested the fan speed switch for output in all positions?
Fan speed default is usually high, as the power doesn't go through any resistance at the block.