FYI: According to my scale, the new 3mm longer chassis is 26 grams lighter than the old one. And after I cut back the chassis guards as recommended with the instruction sheet that came with the chasis, my car was 33 grams lighter than before.

That might not sound like much, but, that is a significant difference in an 1/8 vehicle.

All of the mounting holes are exactly the same except the 4 bolts to the rear diff and the rear chasis brace which have been moved 3mm further back.