Hello yobarry, there is no doubt that the two different gages of metal can be welded successfully. Some folks would possibly say that by changing the gage thickness of the components on your vehicle you may change the way that the car reacts in an accident. Todays cars and trucks take into account many things when they are designed, you can tell that after a crash, many of them aren't even worth fixing, that is mainly because they are designed to absorb the energy of a collision and divert it away from the passengers and thus save lives. Older vehicles didn't always take this into account, many crashes that didn't really look all that bad resulted in some pretty terrible and often fatal results. One other small thing that you may want to consider has to do with the material that the car is made of, todays cars may very likely use high-strength alloyed materials and require a bit more care when they are welded. If you can, get ahold of some information on your particular application, you may find it through I-Car, do a Google search to find their web site and I'm pretty sure they have some sort of forum or technical question section that you could access. Best of luck and regards, aevald