[Keithc8]

Both the 408 and the 427 use the same stroke which is 4.000. This is the way that we build them. So when you go with a Dart block you should just go to the 4.125 bore and get nthye extra cubic inches and make more power. The bigger bore un-shrouds the bore and helps the heads breath a little better as well. You have the same stoke and rod length so the rod ratio is the same. I would not do the stock block 427 which uses a wierd 4.187 stroke with a 4.030 bore and a 6.200 rod length. This gives you a pretty bad rod angle and shorter piston. Once you buy the Dart block it does not cost much more to do the 427C.I. engine. Good luck, Keith