Wanting to upgrade the MTH SD70M-2 I started by looking at the trucks and trying to determine how to bring the sideframes in closer to the wheels. I started with the 3R version of MTH's latest run of SD70M-2's for the Canadian National. After converting the wheelsets to 2R scale wheels using MTH's scale wheel upgrade kit, I immediately focused my attention on the sideframes. I noticed that the original mounting posts needed to be cut back to allow for the sideframes to slip in closer to the wheels, so I nipped them off just higher than the gears to allow for clearance. Later I cleaned them up a bit because they help serve to keep the sideframe off the wheels and gears.
I then focused my attention on the sideframe itself and noticed I needed new holes and to remove some extra material on the mounting posts. I decided to cut slots in the mounting posts on the sideframes to allow for some fine adjustments.. After all this is a proof of concept. 
Once I had all the material removed the sideframe slipped right in. I also used the existing channels for the mounting posts, screws and holes on the top of the truck block to attach the sideframe. I thought it can't be that easy, could it? So I then test ran the locomotive and it worked flawlessly. So I moved the sideframes in a little closer. Still worked, tested the locomotive on a curve (60" radius) still worked! I did the other side of the rear truck. I looked from the top down and couldn't see the brake cylinders. Ahh... Progress! Granted all MTH sideframes don't mount exactly the same way, this quick proof of concept on the SD70M-2 showed me it's possible.
Once I finish both trucks, cleanup all the cuts, clean and repaint the wheels I will take new pictures and post the finished trucks. After completing the trucks I will move on to the pilots! The pilots will get a complete overhaul! After the pilots, I plan on removing PS3 from this locomotive and installing Loksound so if anyone wants first dibs on the PS3 module let me know. After Loksound installation, I will lightly weather the locomotive, take final photos and post a video of the locomotive in operation!
