Back in the late 70's a 40 won it's class (against walker evans none the less) on the Baja 1000.
It was running Turbocharged, propane powered 2F
Honestly, you have to do a LOT of mods to make a cruiser good for prerunning, I would start with something a little less on the heavy side and more on the WB side...
Here is the pic of the FJ40 that was raced in Baja (from Specter's web site). It is sitting in his shop and you can check it out if you are ever there...