you -DO- have a short. and you found part of it when you found "negitive terminal to chassis show about 83.6 ohms", now trace where that 83 ohm short is coming from, then your problem may well go away.
You found -part- because it is a circuit, and you have only found part of the complete circuit. now disconnect the other end of the cable from the heat sink or if it has an insulated standoff and check each of the wires connected there. for ohms to frame. be sure to check the heat sink too, as it has a Mylar sheet insulation under it and has little plastic insulators for the mounting bolts that can cause this sort of short (you may only be chasing a wet wad of dirt, for all we know at this stage, the ohm meter will tell us where it is).
Reading -voltage- to frame has no value other than to tell what cell in the battery is the 'most shorted', your meter does not draw enough current to tell if the current being measured could have enough flow to do anything other than be measured as a 'potential', and even a 6 week old battery will show some voltage to frame, but not much OHMs.
All the cables under the battery, that are covered in white, will need to be replaced or at the very least cleaned and ohm checked. I would replace them all if you are going to keep this truck at least 1 year more, as you will have weird intermittent failures (a.k.a. 'wifs') due to the corrosion saturation of the insulation of these cables. clean out all the corrosion under the battery compartment and check for nicks and cuts where the cables touch the battery box sides and frame of truck
83.6ohms is much less ohms (more shorted) than the minimum of 100,000 ohms I (and GE) said you needed to check for.
Disconnect the cables (that you are reading less than 100k ohms) from every other connection. and check that cable again, and all the other cables it was connected to. Trace the short to it's connection to the frame.