The 340 is out....again.....

FWIW... from the [1965] Plymouth FSM in the small block section for 273 and poly 318....."The bottom of the strainer must be parallel with the machined surface of the cylinder block. The bottom of the strainer must touch the bottom of the oil pan."

Just my thought for why (maybe!): To get max pick of oil and also to provide a little stability to the pickup tube, and avoid any odd noises of the strainer vibrating against the pan on occasion. I installed my /6 pickup juuuuust off of the bottom of the pan and it makes an odd noise at idle now an then that I attribute to the pickup vibrating against the pan. (Can't find any other reason for it...)