You will notice that there is no LS-x into a B-body (Impala car and it's variants):
You will be able to use the Chevelle Kit as a base and find parts as needed to install it into your Impala.
You can not use the Chevelle gas tank (something else that I forgot to include in the motor swap unless you are going to use a carb). EFI requires a high pressure pump to atomize the fuel that is controlled by the engine CPU.
Accessory drive may be useable as is, but I don't don't know what you have as an option (I assume it is similar to the Pontiac G8 sold here in the states). Truck LS has the accessories mounted high over the engine, the Corvette has them all mounted low under the water pump, the Cadillac and Camaro are the Goldilocks (closest to an old muscle car), but there are a lot of parts here in the US that that all interchange on the LS.
Same for the oil pan. GM makes five different oil pans for all of their applications; but none are a direct fit into your Impala body. You will have to either modify your car, or cut and paste parts into the cast aluminum oil pan (easy to do if you can TIG weld), or buy one custom made to fit the older muscle car body which is in the Holley kit.
The transmission cross-member will have to fit your tranny, which may also require a aftermarket flex plate to align everything to align properly.
Holley offers tech support on this product so I would call them for advise on what parts to buy. I used parts out of junk yards here to make the swaps I preformed work: and I relied upon one of my five mechanics who was an LS tunner trained by GM to get it running once I bolted it into the car.