UKPassats

Hey, I blew the 2 front speakers in my b5.5 recently and I don't have much money at the minute, so I've bought some replacement stock speakers from a breaker who just drilled out the rivets and passed them on to me, only paid a tenner which is good, but I don't know how to fit them? I will need to make new holes in the current housing I think as some of the holes have been drilled too far and come out the edge of the casing, to be fair though it might be better to just get new adaptors from somewhere?
I assume I will have to drill out the rivets on my current speakers and use some bolts to attach the replacement ones but I'm not sure what type of bolt to use?
I would love to have just paid for a set of new components all round but I really don't have the money but would love to get these ones fitted so I can at least enjoy stock sound. Can anyone help?

Thanks