No you can’t use the stock Y pipe for the Delkevic cans. You’ll have to fit the Delkevic Y link pipe. Delkevic used to supply two separate link pipes which utilised the stock Y pipe but I don’t think they do anymore. I’m thinking it was because of fitment issues. You could give them a call and see if they have any.
I see someone here recently used wooden blocks between the wheel and under tail to hold things apart while they removed the shock.