Opinions wanted: 408/416 Stroker or 440?

I would go big block hands down.
Get a good bare 440 block and buy a stroker kit, Trick Flow aluminum heads, a good set of headers, aluminum water pump housing, a cam and intake to match your needs, and a good clutch and tranny with 4:10 gears would put a lot of smiles on your face and make an easy 500 H.P. plus.
Sell the 340 to a restorer to recoup some of your costs.
Remember, an A-Body is a whole different animal than a B-Body, especially the weight balance, and the big block was made to easily fit in the B-Body platform...........
I've had several '69 Coronets with big blocks and small blocks in them over the years.
The best one i had was a '69 Coronet R/T with a 440 4 speed and 3:54 Dana.
It was completely stock other than headers, McCloud clutch, and electronic ignition.
That car really went and the torque was tremendous.
Another similar car was a '69 Super Bee with a 440, headers, cam, McCloud clutch and 3:54 Dana.
It was fun to drive and i bet it would beat the R/T in the quarter mile, but it was harder charging on the top end and had not as much on the bottom end, which was to be expected.
The original 383 magnum was all stock and was a lot of fun to drive, it revved quicker than the 440 for sure, but didn't have nearly the torque.
The R/T was a funner street car, and if you build an engine, build it for torque IMHO..............