340 or 408?

If you are building a stroker a lot of folks (including me) used a roller cam. Which in today’s world opens up a lot more options. And roller cams will make more power with more drivability. The bonus of using an early magnum block is it will accept the LA style edelbrocks or other similar heads and it is already setup for a roller cam. There are a LOT of people on her with more knowledge than me..
Make a plan explore all of your options. And select a pathway that suits your needs.. Either way a mild stroker will easily make 500+HP and a similar torque value as well. The torque will be coming on hard in the lower RPMs so no need to run such deep gears like 4:56 on the street..

Best of luck
Good point 408 and 4.56 is gonna be a hard one to hook up in the street :)