Need advice on nat gas to propane conversion on Coleman furnace

LTT

I bought a used Coleman furnace and a kit to do a conversion from natural gas to propane, intending to use it to warm my shop. I feel confident I have correctly replaced the 6 orifices and installed the low-pressure cutoff switch which is tapped into the supply pipe. However, I need advice about replacing the valve's spring and then adjusting both the input and manifold pressures. My confusion comes from the fact that the conversion kit came with one valve spring. The existing valve in this furnace seems to be a dual hi/low arrangement with part #156-4074 (see attached photo). How/where do I replace the spring?


Here's the furnace's model and serial numbers:

EBEBRATT-Ed

The instructions should tell you if you have the right parts and where the spring goes. You also need someone to adjust the gas pressure and do a combustion test.

worldclasshvac

You need a low pressure shutoff too on the gas line before the valve.  Need a combustion analyzer and manometer to set the valve up. You can soot the exchanger up and kill it with improper setup.