You can run non stock heads, like magnum heads on an LA 318 so doesn't really matter if the bottom end is magnum or LA, and OP just states 318, 5.2l is just 318, magnum is basically just a head package not an whole new engine like hemi.
Sort of like the 1968-71 340 is one engine head package and the 1972-73 are different heads and Compression?
We would not be having these long and drawn out conversions if the 'Bean Counters' at Chrysler did not saddle the 318 with sub par parts. If they had offered a 1.88" valve 10:1 with a 252ish cam and 4bbl option on the teen It would be a whole new ball park. Maybe 260 HP at the crank
