Well, to do a 383, you'll need the 350 block. The 305 with a 400 stroke crank only gives you like 334 I believe. They make specific kits for that. The 305 is about a 3.5" bore while the 350 is a 4" bore. roughly. You might wait awhile and see if gas prices still keep people a little antsy about building big motors and if the 350 doesn't come down some.