I'm pretty sure the caravan/k-car 2.6l was a narrow block, but to swap a v6 you would need a new tranny (just to start, not too mention fuel/exhaust/electrical mods). different bell housing. to swap a 4cyl to a v6, the consenus is to do the GM 4.3 engine/tranny/transfer swap from the S Series blazer/pickup (you can find rusted out blazers that still run great just about every where).

-Todd
1987 Montero 2.6l 5-speed (Sold...but I still miss her)
2008 Jeep Patriot Sport 4x4