size

I just got a megan y pipe and I need to cut out the stock ones but I dont know the bolt size that I need, can anyone help? It the 3 bolts that connect to the headers and the 2 bolt that connects to the resonator.

Hi all, couldn't find a clear answer on this question, I'm getting the parts together for a p/s line job, and want to replace the return line with oil resistant bulk hose. Can someone confirm if I can use 3/8th hose on the return line? Thank you