Marc,
Your P4 should be awesome with an LS7 installed!
I can tell you what I'm doing.....certainly not the only (or arguably, the best) route to go:
I have a machinist friend that is doing a porting/polishing job on the heads, installing new springs to match the RPM/lift expected from the camshaft being ground be Comp cams. I'm using Rhoads roller lifters and Jesel J2S roller shaft rockers. I have a FAST 102mm intake manifold and 102mm cable drive throttle body using the FAST XFI ECU and Aeromotve EFI fuel pump system. I am upgrading the fuel injectors to match the intake/cam specs but haven't picked them out yet. Looking for headers but have not found them yet. I have a Katech blueprinted internal oil pump, oil cooler bi-pass block, Setrab oil cooler, remote oil filter, Peterson 3 gallon oil tank, Moroso oil breather/reservoir, Aviad external scavenge pump/pulley on the tensioner bracket, ARE dry sump pan and Accusump 3 QT with electric solenoid for pre-oiling/starvation.
What others do as well might be changing out the cast pistons for forged ones and changing out the Titanium rods. This may be important if you choose to boost. I tracked my Viper with Mike's (MachineWorks) heads and similar setup as described above for my V10 with no problems from the cast pistons. The LS9 has oil squirters but I'm not going to install those even though you can see from my list that I am trying to ameliorate possible oil starvation on hard cornering. Jay has a Kinsler setup for his intake. I'm debating putting on a Meziere electric water pump.
Happy building!