318 magnum VS 318 roller VS older 318 gas mileage

It's a worthwhile question...I'll just add that the price of a decent LA 318 vs a comparable Magnum 5.2 would ne basically nothing. You could get a clean running version of either one for just a few hundred bucks.

Given that it already won't be original and assuming you're ok with the few small considerations needed to run the Magnum motor, I don't see too many compelling reasons to try to find an LA.