I have spare torroids that came with one of the kits,does anyone know the mix and if they will work in a diy stockton bridge for ha,i want to make a coupler for my new manual atu i am building like here :?https://www.angelfire.com/electronic2/qrp/swrpwr.html
Almost certainly not. You will note that the ATU100's own SWR bridge is built on a binocular core, not a toroid. The spares will be for the RF inductor section, maybe mix 2 or 6.
As John said, don't use powdered iron cores for your tandem match. It will increase the insertion VSWR of the circuit, which is what you are trying to measure. Use #43 ferrite.
va3rr