Tony,
I'm going from memory here, so don't take it as gospel (though my memory usually serves pretty well on stuff like this) but while an M62 may be made to work on the Duratech, I think it would quickly run out of breath, especially at higher rpm, given the free-breathing nature of the little 4V V6. I think to properly do it up, the M62 would need to be spun a little too fast for efficiency's sake (and durability) leading me to believe that the M90 would be a far better choice initially, as it could much more easily be spun in its peak efficiency range and make very good power. Not to mention that I believe the M90 is far more common, and less expensive to come by.
