What do I need to disconnect to protect my MSD 7AL-3 while welding on the frame? I know this has been discussed before, but I really didn't want to totally remove the box from the car.

If you’re tig welding I’d disconnect the battery +/- wires, Ignition and Tach wires to the box terminals. Remove the plug wire on top of the coil that goes to the distributor. If your box is mounted to something non-conductive like rubber vibration mounts even better. Remove the ground cable to battery.

Two years ago I took my car in to have the steering knuckles replaced. They ended up welding (tig) a steering support in that I wasn’t aware it needed. Nothing was removed from the Grid ignition and everything worked afterwards.

The only potential problem is when you Tig weld and the machine has Hi Frequency arc starting.

As was described previously, disconnect all the connections mentioned....

Another good practice is to keep the ground clamp of the welder as close to the weld area as possible. If the chassis is powder coated use the battery ground connection post on the chassis as close to where the welding is gonna be done...

I've welded on my car a few times and never caused any problem..... always using a Tig with HF start....

Any welding - I pull the ground connections off all of the electronics. Might not need too but I never had to replace anything either.