Yes there was a brief year or two (iirc) transition period (or 2) on the blocks inbetween the std 70'80/90's LA blocks and the 93/94 mag blocks regarding the oil passages on either valley wall (maybe present but not drilled) the guys here know cuz I've read it prior. that is the main caveat, & if you do use the LA heads & there are no passages you can easily external oil them. EDIT With more thought, there might be something different in the roller/non roller cam situation. Hang loose, some one will help us (iirc it was Scratchnfotraction who is up on the ins and out of em.