My understanding is hydro lifters oil the rockers though the pushrods and mech though the head, am I right to think I can use any pushrods that fit? I sure don't want to ruin stuff by oil starving it
Nope. LA's oil up through the heads and into the rocker shafts. Magnums oil through the pushrods. Check your Speedmasters to make sure they oil through the head. @pittsburghracer knows for sure.
