Wall thickness for frame?

Chassis guys, what wall thickness should I use for my frame?I'll be using 2"x4" It's going under a 33 ford p/u and I'll be building an 8 point cage. Wieght and cost are not big issues, I want to run some big H/P eventually.
Thanks.

 

.120 should do it.

My 32 is .120 including the boxing plates and it handles over 510# of torque just fine. (The front and rear crossmembers are .187 wall - which is common.)
Granted, no slicks etc., but most all the race cars I know about use .120 stuff cept for the roll bar where NHRA requires .134.

Make a point to triangulate well and don't get fooled by the frames that have all the sturdy looking stuff triangulated on each side and the frame sides proper are tied together by only the front and rear crossmembers and somewhat flimsy looking 3/16" plate for the trans mount.

Use several tubes - round or rectangular - for crossmembers and it's a good idea to double up on the crossmembers where the transmission mount is.
Another crossmember for roll bar laterals with seat belt weld bungs welded in helps as well.

Your 8 point cage will help the chassis gain stiffness as well.

 

Thanks C9. I was thinking .120 would work, but this will be my first scratch built frame.(last thing I want is to go too light) I'm planing to sleeve all the joints in the frame. Is this over kill? I have access to a bender, so a round tube x member shouldn't be too tuff.
I scored an axle and bones for the front, so I'm ready to go! I'm sure I'll have a ton of questions as I get deeper into this.