you could put a 5mm long rod on a +3mm vito's stroker BUT you'd have to trench the bottom end because, as Uncagedshadow mentioned, vito's +3 stroker crank only fits into the stock case without trenching because the big end of the rod is shaved thinner to allow it to fit.
If you're going to trench, you might as well get a +4 stroker crank. I've said it before and I'll said it again, I would NOT buy a brand new crankshaft, and then pay to press a brand new rod onto it before I even ran it. If you want to put a 4mm stroker in, just pop it in. Sometime down the road when the rod bearing flies apart, THEN pay to press a new rod onto those crank ends.