Tips on filling Exhaust Crossover

[Mike Taylor 3601]

I started using zinc years ago when a customer brought in some he had bought from Mondello,I buy mine half price of what Mondello got for it,have never had any of the zinc disappear ,burn out or erode or whatever you want to call it. I may switch to aluminum, because I always have barrel full of old pistons.
Do you just use plain old cast piston ?
Mike Taylor 3601