LED builds consist of a few things:
LEDs
Drivers
Heatsink
Then a few odds and ends here and there to put it all together like thermal adhesive, fans, etc.
We carry all the LED DIY parts and im currently about to prototype a board that is plug in play for my 180g. The 180g will take 3 of these boards, your 8' would take 4. Basically all the wiring is done, all you do is add adhesive to attach it to the heatsink and connect the power supplies.
Not sure how quickly you will need lighting but I should be testing it in the next month or so.
www.LEDGroupBuy.com if you need more info.
Check out my sig for LED build (its changed a bunch but it has a parts list of my original design)