attachin front clup to 2x3 or 2x4 tubing?

how do some of you guys do it? do you use tubing or channel? any pix? thanks!

I used 4 3/16 plates on each rail

http://i10.photobucket.com/albums/a105/workin_on_it/3-18-07FrameLayout2.jpg

http://i10.photobucket.com/albums/a105/workin_on_it/3-25-07FrameLayout2.jpg

i use 3/16" plate