In case this helps anyone else, I am enclosing pictures of the result of working with Griffin Radiators to build a radiator to support an LS3 in a 52 3100. While the frame is custom Art Morrison, it is supposed to be "bolt the body on the frame" fit for a standard 47 - 53 body. I will confirm that if I ever finish. The motor mounts are specific to LS3, but the fame support for the motor mounts would also be used for a standard AD motor (I THINK).
We had to cut the "top lip" off of the radiator frame and remove the "X" cross supports. Results below in pictures.
