I want to replace the Northstar engine in my 1996 Cadillac Eldorado
with a late-model GM engine and need to know which GM engines (other
than Northstar) will work in this application--engines that other
people have been successful with for this engine swap. By "late-model"
I mean 1996 or later. I have researched Cadillac Forums--Northstar
Performance and Technical Information at
http://www.cadillacforums.com/forums/archive/index.php/f-23 without
any luck. Searching Google for "1996 Cadillac Northstar engine swap"
(or engine conversion) has gotten me lots of irrelevant hits and no
useful information. I would like a detailed description of swapping
out the engine from someone who knows about Cadillacs and has done it
successfully.
Thank you.

The Northstar uses the GM metric bolt pattern bellhousing.  I don't
know why you would want to but you could use the 2.8, 3.1, 3.4, 3.4
dohc "X" motor, 3.5 "premium V6" for sure.  I wish I had looked
closely at the belhousings of the LS1/LS6 motors when I worked for GM
because that would be the best swap for the size vehicle you have.  If
they use the metric bellhousing then they will work after modification
for starter postion and a lower bolt hole.

have you researched this at http://www.lincolnvscadillac.com ???