Some of those systems should have onboard controllers, no? The G5 models may have PCIe cards (Smart Array P400 is most common), but the G6 systems should have Smart Array P410 models embedded on the motherboard.
You're dealing with two generations of system, though. The G5's have different drive bay and controller connections than the G6 systems, so I would not lump the DL360 G5 and DL360 G6 together. The G5 ProLiants have SAS SFF-8484 connectors internally. The G6 ProLiant systems have SAS SFF-8087 connectors internally.
They are vastly different systems. Can you provide the specific controller model installed in the DL380 G5, and what spare parts you have available?
Edit: I'm assuming you have a Smart Array E200 controller in the DL380 G5. That controller does not support RAID 5 unless you add a Battery-Backed Cache unit (BBWC - #351580-B21) to the controller. Without going into the issues with deploying RAID 5, that part is all you need in order to make the DL380 G5 do what you want. If your G5 DL360 has a P400 or P800 controller available in PCIe form, you can move that over to the DL380.