318 build with dyno session

Stock top end stuff isn’t being used, so that isn’t a factor in this discussion.
My point is there isn’t any difference in power if either block is built with the same parts. Aftermarket pistons are going to weigh the same in either block.
The only difference is in what heads you choose to put on one or the other. You can put better heads on the LA and it will run better, you can put better heads on the magnum, it will run better.
You can use the same heads and they will run near identical