The K-member isolator bushings have nothing whatseover to do with supporting the weight of the engine. The front suspension does that, and it's completely anchored to the K-member. The bushings simply insulate that assembly from the body. Any bushing material that flexes allows the frame rails to flex independently from one another, which negatively affects the already iffy (at best) handling of the FMJ front suspension. That's why both the Mopar service kit and the MP mounts (same kits, different part numbers) were made of cast iron. It's still the best option if you can find it, and even with those in place the ride is still more cushioned than in any A, pre-'73 B, or E body. There's almost enough rubber in the stock FMJ front suspension to start a tire company. :eusa_doh: Personally, I won't consider anything but solid metal isolators for my own car. If I have to make them, so be it.