the 200 4R is farly common in the wrcking yards... cuttlas monte carlo, all the clones...pretty much all of them were 200 4R equipped. Just look for the tranny mount being all the way to the back and the pan covering the whole bottom of the tranny (to the crossmember).. look at the chart on the link.
http://www.maliburacing.com/auto_tranny_id.htm