x2 I'm assuming he means Gen. 3 (new hemis) but regardless of generation it's quite an extensive and expensive operation. Magnum 360 swap is a walk in the park by comparison.
Cheapest would be gen 3, then gen 1 (including hard to find parts), final gen 2 (just think of the 572). In the end the gen 3 would probably the lighter of the gens and la blocks