Quick and dirty on my 360:

'97 5.9 Magnum complete from a truck, 87K miles
Scott Brown cam 226/238 @ .050, .520"
Three angle valve job, machined down valve guides to accomodate higher lift
MP valve spring and retainers
Crane roller rockers
Eddy Air-Gap intake
Eddy 650 AVS
1 5/8" Hooker headers

Put this in my Demon and on my 7th run I hit 12.76 @ 105.5. Remember this was not only the cars 7th run but my 7th run as a driver. The shortblock is 100% untouched. I used the original pistons, rods, crank, bearing, rings, even the oil pump. I never even took it apart to inspect it. The cylinder walls still had crosshatch in them. I paid $700 for the complete motor from a local JY, I paid less than $2000 for the balance of the motor. Seems pretty close to what you're looking for.

Compared to the old MP 380 horse Magnum I have a larger lift cam and roller rockers but it uses a 750 cfm carb and 1 3/4" headers. I still believe that I have 400 horse. With the larger carb and headers I bet I would be close to 425.