83k for $500 seems like an average price...might be able to find something a little cheeper if you look harder. look on car-part.com all the junkyards list their shit there, i got my 4l80e from there. also 83k that t-case should be in good condition...you could just get it, change the fluid, and throw it in. i would open it up and replace the clutches if its autotrack and gasket obv while its out of the truck if you plan on keeping it for a while...