Simple one really, how do the Imperial and Chaos Land Raider kits vary in contents?

Afaik the Chaos one is basically the same tank but with the Chaos vehicle sprue tossed in.

I ask as im planning on knocking up a couple of Heresy Era Land Raiders, and could do with the Combi Bolters and Mk5 head, but dont want to lose anything vital to making a loyalist tank!