I'm sure a 14 bolt girdle could be put on a SII block. Just not sure if there would be much, if any benefits. It would definetly cost some $$$ to put one on a SII block.
IMO rather than going thru the process of putting a girddle on, maybe you should see about doing a little 'block filling'. I have heard of guys doing a 1/2 fill for applications being run on the street with no cooling problems.
Just another avenue to check into