Could go either way, I forget which(stock) rods were used/between the 258 and the 4.0, if one or the other is used you can just reuse the stock 4.0 pistons. I think the combo for that is to use the 258 rods and 258 crank, then stock 4.0 pistons are used, if you run the 4.0 rods you need custom (but not that exotic anymore since more people are doing this) pistons.
