4 x 4 and 2 x 4eng mounts are totally different from one another.
what you are describing in yours sounds correct. some of the later perches will mount in their place to takke the later insulator( the one that has the horizontal bolt running through it.
perhaps this link will help you, http://www.speedwaymotors.com/LS1-Motor-Mount-Adaptors,5070.html.
if not check some of the aftermarket shops as most will have something.
http://advanceadapters.com/product/3961/(P/N-713088-P).html
ron
