360 to a 408 how much quicker

I agree. Actually it's a "total" combination working together- engine, trans, rear, suspension, tune-up, etc. I've gone 11.31 @ 115 mph weighing 3,540 lbs with a 360 +.060"., normally aspirated. (No NOS.)

Unported 1.88" OEM heads.
10.5-1 compression
.474" lift hyd. cam.
750 single 4 barrel
904 trans - footbrake.

There are other, similar cars, including lighter combos and Magnum 360's, that have been in the 10's!

I don't mean to brag, just trying to point out that you can find a lot of ET through fine-tuning, selecting the right parts, understanding how each part works alone as well as together with everything else, etc. All the cubic inches in the world will not help you be much faster if there is a weak link, mismatched part or bad tune-up in your combo. More cubic inches does provide more potential to go faster. But it needs time, patience, work, understanding and a good machine shop to get the most out of it, OEM size or stroked.

how r u doing this?

i should have 400hp to run 12s but i want low 12s