It's a quick way to ruin a good set of running boards, and if the pipes are mounted rigid to the cab corners, you'll need to run at least a short piece of flex pipe from the bottom of the upright pipes to the ones going to the exhaust manifold. There has to be a little movement available since the engine/trans is mounted in rubber. Flex pipe wears out and/or leaks in a very short time, so you'll be fixing leaks often.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!