Don't know for sure, but look into a 3800 from a Buick Regal.
I'm looking at a 350 swap right now, I have the engine, just haven't taken measurements. Fortunately, I always drive manual, so all that will be required will be (hopefully) a bellhousing swap (mechanical) and computer swap for electrical.
Whenever swapping engines, electrical is key. I believe a 3.4 will swap right in, without any changes, but no quotes here.
Steve