Magnum head and exh manifold ID

According to the "How to build big inch Mopar small blocks" book 1992-2003
magnum heads can replace the 1967-1992 LA heads. The increase in airflow
can gain 20 to 50 HP depending on the combination. There are 2 major differences between these two: the magnum rockers oil through the pushrods
whereas the LA oils through the block,around two headbolts, and up to the rocker shaft. The second difference is that the Magnum intake manifold bolts to the head vertically and not at a 90 degree angle like the LA heads. You also have to use Magnum valve covers because they have 10 bolts instead of 5.
If you're planning to put Magnum heads on a LA you will need Lifters from a v-8
AMC, hollow pushrods (Mopar Perf. #P5007477) Magnum head gaskets (to block off the oil holes)the Magnum head bolts, and an intake manifold for a carbruetor.(all Magnums are fuel injected) There are only three intakes available for this conversion, Mopar# P4007381, Edelbrock "Air Gap" #7577, and Professional Products "Crosswind". I also looked to see if the 5.2 and the 5.9 heads are the same. They are. (60 cc. chambers,1.920" intake valve/ 1.625" exhaust.) The Magnums have a 10cc smaller combustion chamber which will raise compression about a point. They also have larger ports and bigger/lighter valves.
I have been studying this combination as a temporary replacement for my tired old HP273 in my 66 Dart. I found a good set of heads for $20 and a mid 80's junked out Chrysler 5th Avenue with a good running 318 LA for the cost of towing and labor to pull the motor out. I thought I'd give it a try. By the way, If you want to install the Magnum in an earlier a body v8 car the motor mount tabs are on the block for both new and old applications and the transmission/bellhousing bolt circle is the same. Boy I better get to work b/4 I'm late. Later and good luck!
toolmanmike