rear subframe

aight i got a 69 c-10 where the cab is i already stockfloored it with 2x4 1/4" thick metal the back half is stock frame other than a c-notch my question is "Would 2x4 3/16" metal be over kill for doing the back half ive been told by a few that doing 2x4 quarter inch throughout the frame would be over kill so would 2x4 3/16" be fine or would it also be over kill and if so whats my next option 2x3... but that would look kinda gay two different sizes of box tubing... some help would help on my d-lima

2x4 .120 is fine.

to give you an idea, prostreet cars, like mine on my profile, are built out of 2x3 .083 box tubing, unless of course it is full round tube, then 1 1/2 .065 chrome moly works real nice too..

so is 3/16 2x4 just building a tank or is it fine

cant go wrong with over building something man, if you dont feel good about one size, build it bigger. 2x4x3/16 will def be beef.

If you already went 1/4" on the rails, I'd go with the 3/16" on the backhalf. It is going to be beefier than needed but like Dave said, "cant go wrong with over building" unless it's a boat maybe. Depending on how your designing the frame, it may cause a flex (stressed) point at the joint of the 1/4 and say the .120". On my dually, since it's not a full frame, I built up the transition about a foot in both directions. It's actually similar to your 1/4 to .120 change except the stock frame isn't boxed so it flexes a bit more than your 1/4 boxed.