Neighbor is fixing up 1977 Ford ltd. When installing new battery he hooked it up backwards. Engine will now crank but won’t start. What was damaged?
Given a 1977, it’s a good bet that the voltage rectifier was fried in the process. Those things are sensitive. My knowledge is derived from motorcycles, but I do know that if you hook up a system backwards then you stand a good chance of killing that thing because they send the juice one-way and you can bust it wide open if you’re not careful.
Get a second opinion though.
The electronic ignition module was fried, that’s why it won’t start. Fortunately, they are pretty cheap. Also, there is a good chance of damage to the voltage regulator, and to the alternator.