Here is how I installed Mario's kit. It is not terribly difficult but it is time consuming. I think it makes a significant improvement in the appearance of the engine and is worth the effort. Thanks to Mario for building these kits. Here is where you can purchase them. This may not be the "right way" to install the kit, but it worked for me. I hope it helps you out if you have this project on your to do list.
Once you get the trucks off unscrew the pilot and separate. 
Unscrew the electro coupler and clip its wires.
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Next I used a cutting wheel to cut off the OEM pilot mounting tabs. I used a bench grinder to take it down behind the flange to ensure adequate clearance. BTW I removed the pick up roller assembly and the front wheel before I starting cutting.
Another view of the modified truck. Reassemble the pick up assembly and lube the roller and axles while its off the chassis.
Next you have to prepare the OEM pilot. Dremel off the rear mounting tabs.
Tabs now gone.
I used a little glue to locate and set the spacer on the bottom of the chassis. Note that the flush side of the shim is down. The top side has a ridge the you line up with then end/corners of the chassis.
I drilled hole and then tapped it. I also drilled out the holes in the kadee draft gearbox. You can see the ridge on the topside of the shim, it outlines the chassis slightly.
I slid the kadee into Mario's pocket, lined it up with the glued down shim and then tightened the screw a couple turns.
Next I drilled through the front hole of the gearbox and into the the shim.
Next I separated the previously glued shim from the chassis and ran a screw in the forward hole of the draft gear box into the shim. The screw must not protrude past the top of the shim.
Flip over the chassis and bolt through the rear hole of the draftgear box into the previously drilled and tapped hole. This bolt holds the modified assembly to the chassis. I used a little CA for good measure. Don't over tighten or the assembly will not sit flush to the underside of the chassis.
Dremel the bolt off flush to the chassis so the shell will sit flush.
Repeat the process for the other pilot and put the shell back on. I slightly bent up the coupler "hose" and dremeled off a bit of the end to prevent from shorting on the center rail.
Here is the finished product......
Kevin
