The last time I built a bar was 8 years ago. I know for mild steel, it had to be 1-3/4" and I believe it was required to be D.O.M. is that correct? No welded tube? Also what is the wall thickness required? Thanks.

It does not have to be DOM, .119 wall IIRC. Mine is .134 I think.

I finally found the rulebook online and mild steel is .118 but I imagine .134 is better for thickness in the bends. Is welded tubing acceptable? NHRA does not require DOM, but I would like some opinions on the welded tubing. Thanks. Lee.

Rule book says minimum of .118" wall thickness. 1 3/4" diameter.

Most kits are ERW .134. The reason is that ERW is not nearly as accurate as DOM or ChromeMoly and has to be purchased at that thickness in order to be sure to meet the spec. I've seen .120 welded seam as thin as .113-.114 and .134 down in the mid .120s. .120 wall DOM will usually vary maybe half a thousandth one way or the other.
Also, DOM is typically 1020 steel where ERW is usually 1010. You can tell the difference just running a drill bit through it.
The only advantage to ERW is that it is considerably cheaper and it should be. Personally, I won't use it.

Thanks for the replies, especially about the type of tubing. I bought dom and bent it up myself for the last one and it came out very nice, I was not aware the kits were welded tubing, but that explains why they are so cheap! Thanks again!

Most are, you have to pay attention to what you are getting.