[Woodz428]

There's a 0.20 difference in stroke(0.10 at the top & 0.10 bottom), I think you would have to have a really tall block or the pistons would require cutting to keep them from whacking the heads. The 410 variations should be available from several sources, I wouldn't try screwing with 390 pistons to get the correct height...that's a pretty thin piston top after that much machining, IMO.