Hi Akiel,
My recommendation would be to use the NI PXI-2567 64-channel external relay driver and external relays.
The PXI-2567 is capable of providing up to 50 V or 600 mA of drive capacity (with an external supply). Internal drive power is 5 V at 1.25 A, 12 V at 0.5 A. The relay driver is the ideal choice when the current and voltage requirements for relays are greater than those found in existing switch / relay modules. The PXI-2567 includes overcurrent, overvoltage, and flyback protection to ensure long-life operation.
3rd party relays that can switch 43 A at 28 V can be found by perusing relay manufacturer or vendor documentation. Below, I provided two available hardware options that I believe are suitable for your application. I would verify this is true with the relay manufacturer, as they may have additional questions about your specific application.
Panasonic High Capacity Relays
http://pewa.panasonic.com/pcsd/product/pwr/index.html#05
Omron DC Power Relays
http://www.components.omron.com/components/web/webfiles.nsf/products.html
Hope this helps!
Chad Erickson
Switch Product Support Engineer
NI - USA
