Both are sweet blocks. Dart is a bit more expensive then the Merlin. If you want some sweet deals on this stuff, check out Dynoflo on Ebay, he is an e-bay retailer. I know Shawn Spickler got his 540ci short block from them. He goit the Dart Big M block, Eagle ESP forged H-beam rods, Eagle ESP crank, SRP forged pistons and some C&A (I think? /forums/images/graemlins/dunno.gif) rings. The whole deal was like $3200 assembled and shipped, IIRC. THats a Hell of a deal IMO, since that block is abouit $1950 by itself