318 temp use

Hang on,
I only mentioned headers cuz, I assumed you were gonna run them on the stroker. You're not gonna run 340 manifolds on the stroker are you? I don't see the logic in that.
In a stroker, you're gonna run something like a 284 cam, and with that od trans, a wide LSA, So maybe a 284/112. This cam, depending on the grind, would have 60* or more of overlap. Overlap can be like a supercharger with good working headers. That 284 wants headers. Without them the overlap period will not contribute much to the output of the engine. Of course a 408 would probably not miss the top end power cuz , well, it's a 408,lol.And you can only wind it up now and then on account of,well, speed-limits sorta get in the way.
But suppose you run a 268/110 in that stroker to make monster torque. Well, this cam still has 52* of overlap, so it will like headers too! But with all the torque this combo is gonna make,and the 3.09 low, you can run 2.94s, and hit 60 mph at the top of first doing 6500 with 28s. So headers aren't gonna do squat on a combo like that, on account of you'll be spinning all the way.
So I kindof get what you're thinking.