That's what I ran into ! if I had ran the stock LA heads the 821s would of been fine due to the top end oiling as the mag heads on La block will block off the oil supply and only relies on oiling through the lifters ,hollow push rods. I've been using the 801s on mine and have put on around the 15k on the engine with out any issues, gets plenty of oil up there .I'm not sure what rocker gear you are using and make sure your push rods isn't rubbing up against cylinder head as you might need to grind some material, not in all cases you just need to check and one more thing invest in a push rod checker to determined pushrod length !