73' 351 Cleveland Charging 17v

I restored this car back in 1997 and rewired the connectors to the voltage regulator because squirrels had chewed the plug off. Everything had been fine since then until last month I started having issues. I checked the voltage charge of my battery while the car was running with first a battery tester then a multi meter. It was fluctuating between 12v and 15v, so I checked the voltage regulator connectors and there was one frayed wire and some corrosion. I bought a new voltage regulator and a new plug, when I finished installing them the charge was no longer fluctuating but it was overcharging at 18v. I plugged up the original regulator and it was also overcharging at 18v. I read somewhere that the voltage regulator has to be grounded to the body so I bought new bolts and ran a ground wire off one of the bolts to the shock tower bolt to ground it. I cranked the car up and it is still overcharging at 17v, even after it idles down, or when I rev up the engine. I'm not sure if one of the plug wires for the regulator had to be ground or just the body, any help would be appreciated

I had to replace the original battery it got cooked, and that's when I realized I had a problem after I replaced the voltage regulator and the plug. I have tried to research the location for a ground on the voltage regulator but I cant find one. The only thing I can find out is that some of them ground to the firewall, was hoping someone could tell me how to properly ground out the regulator, if it is a wire or something else I may need to do. I'll try running a ground wire to the negative post from the body of the regulator. I'll also unplug the regulator and see if the battery is still overcharging because that may mean a wire may be grounding that shouldn't be or a problem with the alternator I think.

If anyone viewing this thread has a picture of what the ground is suppose to look like or how/where I am suppose ot attach it that would be awesome

So far ive tried running a ground directly from the negative post to the voltage regulator. Tried sanding the black paint off of the inner skirt to get better ground contact. Replaced the regulator pigtail plug wires, I even replaced the alternator and nothing has worked. The regulator that I have on there is brand new and I have the receipt still so I will try returning it tomorrow for another one. The battery reads 17v while the car is running( I only leave it running long enough to test it with the multi meter ) I have also used the multi meter to test the alternator by placing one lead on the batter connector on the back side of the alternator and one on the negative post of the battery. I get a 17.9v reading from the alternator when the voltage regulator is plugged up and a 12.5v when it is not plugged while running