Trying to get 400hp from a 360

IMO, you'll not need alot of cam to do this and most of your stock parts will be re-used.

From top to bottom;

750 cfm carb
RPM intake from Edelbrock
OE heads bowl ported w/bracket valve job w/2.02/1.60 valves
KB107 pistons. Comp ratio is pump gas freindly, not to exceed 10-1 but better than 9.0-1 This piston and head combo is probably good for a 9.8-1 ratio with a .040 head gasket. These pistons need not be at zero deck, but should NOT be a positive deck height at all. Slightly dwon in the hole is OK. Less the better.
New connecting rods can be purchased for cheaper than re-working OE rods.
A "Default 400 HP cam" would be a Comp Magnum cam @ 280 advertised, 230 @ 050 duration, .480 lift on a 110 centerline.
Headers into a 2-1/2 exhaust.
MP distributor and a high powered ignnition

tune this well and you'll have 400 hp.