Piston slap is not a product of a forged piston. Piston slap is a result of too much clearance between the piston and the cylinder walls.
You can run forged pistons all day in a pump gas daily driver and they are just as quiet. Forged pistons take the abuse of detonation better than a hyper...
Any block I ever do with studs or bolts I chase and clean out all of the head bolt holes.
You need all the grip you can get from those head bolt holes. (Stop laughing.)
I have used a Comp 58/58 triple ball bearing on a bone stock car and had pretty good response and there is no lack of power with it.
I used one on a forged 3.400 crank/ 3.810 motor with ported heads running a flat tappet cam and there is no damn lag at all with that thing. And yes the top...
At bare minimum you need a bigger fuel pump, 50 pph injectors are good for 600 hp and your turbo is good for about the same. Make sure the wideband is working you need it.
That MAF is not the greatest to use at 600 hp, you should get at least a Translator plus or go to a spped density set up...