It wasn't really a "clean sheet" design, such as the LS series V8 is to the old small block chevy. It was in fact the highest state of evolution that the Buick V6 attained before it was discontinued. The last mods to the block construction design were in the late 80's, when the block changed to a more "on center" style which means that technically you probably could get LC2 heads to bolt onto the block, but there is no intake manifold to use to hook them together. When GM powertrain morphed the Buick V6 into the 3800 the "on center" spacing was the first big change. When the Series 2 and 3 came along, there were further changes to deck height and then cylinder head design such as the order of the valves which make cam swaps tricky too. Some of this I learned playing with a Series 1 L67 from a 95 Riviera and the rest from asking questions around here and other sites, along with wrecking yards and measuring tapes.
Bottom line is, its not worth using the LC2 hardware if you have to custom fab an intake and custom grind a cam for the right spacing, etc... Better off turbocharging the 3800 engine I think. The heads can be made to flow very well and there are strong crank/rod combos to be had as well.