I just reread some replies... somebody said "bent needle"... I'd like to see that, because there is no way to bend an amm needle. The needle doesn't have anything to stop his movement into the gauge, but is attached ( by friction/pressure ) to the counterweight what moves to the magnetic field created by the load running throught the ammeter. Worst that could happen to the needle is loose the indexing getting free from the counterweight. This is a proove lot of ppl doesn't really know about how it works this system and their comments play on several boards like true statements and myths.
About the ammeter reinforcemement. This is a job I made to a 70 Charger in Venezuela which was getting constantly without batt charge and I had to get back it on the road couple of times... sure, the studs were loosen from ammeter inside and it was really close to get shorted to ground due the insulation conditions, althout pic is not mine and I found this pic years later I fixed the Charger 70 ammeter.
On this fix, who made this job made and suggested to part out the gauge to not affect to the magnet quality when heating the brass and studs to stick the lead, which could affect of course the gauge appreciation/calibration. Actually if the brass and studs are clean enough or if you clean them enough using the soldering past or even some sandpaper or dremmel stone if studs are already loosen, you won't need a lot of heat to get the lead attached to the parts soldeing both pieces. Is what I made on the ammeter I fixed and worked like a champ after that. I used a 40W soldering iron. And didn't need that ammount of lead like the one on pic.
After this job and getting the propper Alternator, contacts on ammeter are solid enough to allow a good current path without any risk of any heat on them to melt the lead, since the resistance posibilities is close to zero.
Then of course refresh the ammeter insulators to the cluster housing ( inner and outer ), clean stud threads, nuts, eyelet terminals to the wires running to ammeter and VERY IMPORTANT: when tighten up the amm nuts, HOLD THE LOWER NUT WHILE TIGHTENING UP THE TOP NUT. Two wrenches for this or a wrech and a deep socket ( 3/8" ). This is another tipical mistake made when reasembling ammeter. The bottom nut barelly tights up to the cluster to keep the ammeter in place THEN you tight up the wires BETWEEN NUTS, not against the cluster. If you don't hold the bottom nut will make to spin the studs inside bending the internal ammeter path to the current ( &/or will break the insulation), loosening and once again, getting a new ammeter problem... then will blame again to the gauge and not to the assembly procedure.
BTW... I think this same pic I'm using to show the soldering job was made from the same thread somebody mentioned here about using brass sleeves on studs or something like that. Actually no need for that, but quite enough to solder these ends to refresh the ammeter life. I think the thread was called "bullet proof ammeter" at dodge talk forum or something like that.
Once again, no need this ammount of lead shown on pic ( sorry, blurry pic... it is what it is ), but just enough to keep the studs and brass contact without any resistance probability, even better cleanning internal surfaces to be sure the contacts are on internal faces and soldering once get hot by the soldering iron. "Leading" first the surfaces, then getting them together and heating will require less heating time to get them soldered.