here are some pictures of a custom set i just finished for the 76 build up of fellow list member bmcqueen that i've been working on (and am almost done with!)
they are a bolt on set up. i machined up some mounting blocks that got welded to the frame sides and the bars have plates that bolt up. i notched them to clear the stock rocker panel and still be tucked up. this way they could be removed easily.the mounting blocks could also be easily removed from the frame and you'd never know they where there.
2x2x .250 sq. tube with 1.5 x .125 round. all tig welded. nice pieces. pretty straight forward to make, just takes time...
enjoy~
nick