I can answer this one.
Most kits do not have enough clearance. You can modify yourself but you are legally liable if it fails and someone gets hurt.
Manufacturers design kits that go toward the highest sales to keep the costs down.
The majority owners want a Chevy V8 and slam the truck to the ground so this is what is marketed.
If you want the stock inline 6 and somewhat close to stock ride height, you need a rod shop.
Scotts Rod Shop makes these parts but last I heard they only sell to rod shops now. Not to individuals and certainly not me.
I am banned (well politely asked to leave them alone) because I kept asking questions about liability and insurance.

"Adding CFM to a truck will only help at engine speeds you don't want to use."
"I found there was nothing to gain beyond 400 CFM."