Check the chamber volume on the Y's, get them milled to give you whatever compresion you want. Have them flowed and ported, three angle valve job, and if they are stock springs CHECK THEM. They had a bunch that didn't have good springs at all. They'll perform well though if you just do a little work upfront. I learned my lesson by bolting them on a motor with no prep, the results were not good. Ended up having to take them off and re-work them, after that things were fine.
Ron