Really anything over the one inch you are into firewall surgery with the diesel. All the 2" kits say right on them, " not for diesel engine" , they don't sell 1" kits, which is why we have resorted to the hockey pucks. Not so dumb now , eh?
You can buy pucks by the half dozen and the dozen from hockey supply places online dirt cheap and they are high quality hard rubber. I used some nice big fender washers from Ace hardware that matched the puck size to distribute load wear on the things, and they are wearing nicely
That 1 inch gets you extra room for turbo and tire clearance and just enough to get my big fat gullet under the running boards without having to run the thing up on ramps
Only modification I needed to do with mine was to cut out the bottom of the fan shroud a bit for clearance