L6 or L8 loom will be fine, just need to swap a few wires that's all, can also use the L8 ecu if you want as it is better than the L6, personally(money dependant) I'd ditch the std ecu's and just go aftermarket, never looked back since I did.
There is 4 or 5 connections needed to connect the engine loom to the car so dead easy.
If you are even thinking of a coilpack I would seriously look at prices of everything, it is possible to get a NEW ECU new loom and mapped for £500, so no point if hundreds on coilpack imo then £500 for msd setup on top, the ecu I think is from m tech, advertise on pf do a search, vastly better value imo, this isn't the ecu I went with but is a very good ecu from what I hear.
tabetha