i'm putting a mechanical cam into my 289 ford and i thought it would be a good idea to get hardened pushrods. however the catologe i'm looking at says that they are used with slotted pushrod holes in the heads or guideplates. i'm pretty sure i don't have slotted pushrod holes, so would i have to buy guideplates to put these in? i would think that non-hardened would need guideplates more than hardened. also, do i even need to get hardened or new pushrods at all? thanks.