150 HP LA 318 - vs - 230 HP Magnum 318

Nobody has really brought it up yet but a Magnum 318 will also get noticeably more gas mileage than the LA version thanks to the roller cam and heads even if the intake, carb, exhaust, etc. is the same. Also if you are building one up you can safely run 10.5:1 compression (static) in a Magnum which is what you get with a set of zero-deck flat tops. My Magnum-headed 360 with KB-107s runs fine on pump 91 and the timing is close to optimal. An open-chamber LA engine can barely handle 9.5:1 on pump gas without pinging or making too much heat. Overall Magnums are more efficient so you can make more power AND get better mileage if you like to drive your A-body a lot.

The only good reason IMO not to choose a Magnum over an LA is due to the cracking heads issue which is the case with most used Magnums... and even then I'd just get a pair of EQ replacement heads at $300 each, problem solved!