Ok I have done a bit of asking around and checked a few things out on my truck to find the cause of the rear main bearing failures that I have had.

One of the engine guys that I deal with had seen this before and suggested that I check the engine mount is flat, as this causes the crank case to warp and stresses the bearing causing it to fail.

I have just finished checking the mount that I had in there and found that there was a small amount of wobble in the motor when it is on the mount and that the top blocks were touching the side of the crank case. This happened on both the motors that I tryed.

So I put the standard mounts on (for the first time in the truggys life) and the wobble went away. At the moment the root cause appears to be my engine mount. This will take time to verify as the failures were a few months apart and we are now moving into winter here.

I am still working out what to do with the quick change mount that I just took off, and I also have a king headz extended mount now to.

For anybody that is interested this article gives an overview of engine mounting:
http://www.massivemods.com.au/produc...roducts_id=352

Thanks for the help I will try and keep this updated