318 stroker -> Mopar Performance A8 build guidance needed.

SOMMS said

Lessee - I'm using the one posted at Hughes Engines (https://www.hughesengines.com/TechArticles/5engineweights.php). And aluminum heads are going to be used no matter what (trick flow v W9).

That puts the 318/340 in the 475lb zone(with alum heads).

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While those are still "approximate from various sources", the relative differences are the same, dressed or assembled long blocks. I considered what You are only using the "R" block LA version, but unless it's going to make $$$$ for You, the return isn't worth it for the weight savings.
I wouldn't buy the trans until You've actually decided on the mill, torque band/rpm range should be known so the gearsets & rear gears can be picked to compliment them.
Might want to peruse Racing Junk for old ARCA NAPCAR or other series stuff where Mopar pulled out long ago, it went somewhere, l would go with as much displacement as possible if You want this project to do some kind of dual-duty at that output level.
Best of luck.