This link has some good info on the stock design motor mounts:
http://www.persh.org/pickup/perches.htmThe link is down at the moment, but it was up a few days ago. Maybe it will come back online.
Here is a web archive of the page:
Wayback MachineI think the most interesting thing from the page is that the auto and manual transmissions had different motor mounts. You probably need the automatic style mounts (assuming you are trying to stay stock-ish) which are pretty uncommon.