Never seen it done on a Z, but there are several E46 threads out there experimenting this.
I believe Mishimoto was making an aluminum replacement but it was of poor fit/quality and was discontinued. There is however an outfit called Zionsville Autosport selling a comp radiator and expansion tank setup for E46; you might try contacting them about a solution for the E85/6
https://www.zionsvilleautosport.com/...g-kit-1999-05/