Where do I get struts & springs for a Datsun Roadster with a chevy 350 engine?

H, I take it by not relaying a year, this is a home setup that was custom built? If so, I'd suggest you find a way to take it to a local suspension shop and have them weigh the setup, including how many will be riding in it, and they will be able to make custom springs to match up with already manufactured struts or shocks if you prefer shocks. This is what we've had to do with the many competition audio setups we have done in the past due to the weight issues in smaller vehicles with multiple and large sub setups, including the amps, batteries, and hydraulics. We've also had to do this type of setup with the mulitple 30 and 31 model A's that we have modified. All turned out great! Good luck, and what a RIDE!