Sheet metal thickness question

HI All-
I know this is real basic stuff, but:
I was wondering what gauge sheetmetal you prefer when welding in pacth panels to 40's -50's bodies. I am trying to determine the thickness of the metal on the '51 Merc, and it seems to be 18 GA. Does this sound right? 16 seems too thick. Thanks-

 

18 ga is better because it's about as thick as you can go with most bead rollers, etc without getting into the professional equipment...

 

I took a few leftover pieces of sheetmetal from my 51 Merc to a big heating and air fab shop when I was looking for metal to put in behind my rear window.Some of the pieces did vary a little,but when they measured what I had,they came up with 19 gauge.I bought a few pieces from them,although I had to remove the galvanized coating before I used it.Not sure if 19 gauge is common or not,but this shop had it in stock.Not too thick,not too thin,just right..

 

18's good.

 

Yup- 18cold roll for body 16cold roll for floors and forming hammerformed corners-
If you are not "beading "the floorpanels I suggest Hot rolled as its "stiffer" and warps less when welding......

 

is 16 guage hot roll proper for patching just sections of the floor? my trans tunnel and rear floor is great, but the outer portions of the front floor panels is shot to hell. i thought about using 18 guage and gussetting it, but it sounds like 16 guage hot roll would be alot simpler.