That ladder device might work with some square tubing and welding. I installed one on the outer "C" channel of a small dump body. The ladder slid between the frame and dump body when stored.
Pre-bent lines are also bent to fit into the packaging and don't always straighten out like needed. I put pre-bent stainless in my old 2005 Sierra, would only use them again on a bare frame. There was too much stuff in the way for easy routing resulting in mass consumption of adult beverages.
I've employed two always hungry barn cats, one is 13lbs. the other 16lbs. Even though I feed them in the morning, several times a week they'll leave a DB near the back door. Well worth the investment.
Use starting fluid if you want to blow the head gaskets. 6.2's don't like to start without functioning glow plugs or fair to poor batteries spinning the starter. It probably still has the 24 volt starter & glow plug system. Get a multi meter and figure what's 24 and 12 volt.
I vote for one of three things; valve guides, head gaskets, or rings in no particular order. If the smoke lessens, valve guides. If the smoke smell "sweet" or bubbles in the radiator, head gaskets.