Originally Posted by tecgod13

Remove the dead battery, as you say its only a big resistor now. Make sure you insulate the positive battery clamp from that battery so it doesn't short against anything.
If there is a block heater, plug that in for an hour before hand to get the block and coolant warmed up. You can also aim a hair dryer or heat gun into the intake to help warm things up.
Best option is to replace with new batteries, but if you can't at the moment and just want to move it around the yard i can understand that. Try to get the one battery charged as much as possible before you attempt to start it. You can get better jumper cables, or use multiple sets to divide the load. The batteries in your truck are strong enough to start the ambulance, just need big enough wire to get there...
You can also use another vehicle with its own set of jumper cables along with your truck to get more oomph to the vehicle, but honestly you probably need to get a good set of jumper cables.