What about multiple servos (like,Ibelieve, the LST) ? If the ENTIRE car is 60 lbs that doesn't mean that the servos are pulling 60 lbs. They are just turning the wheels and pulling throttle linkage. TheBaja 5B is 3 feet and weighs around 30 lbs. Couldn't you find a way to double up two of those servos. I may very well be wrong, but I saw your thread and the thoughtoccurred to me.

Also, check out the threads is the GiantScaleforum, a couple guys were working on 1/2 scale and 1/4 scalecars. I don't remember the namesof the threads, but the guys in there are very knowledable about large heavy RCs.