If the second coat is flaking off alot I would definitely strip it. It would take you almost as long to DA the entire truck if the flaking is bad. Flaking usually means that the proper prep work wasn't done on the last repaint and will come back to haunt you even if you feather out all of the flaking areas. Has there been any major bodywork done to it? This can also complicate things because the stripper will eat the body filler and you'll have to grind it off and start from scratch again. Buy a gallon of Aircraft stripper a gallon of lacquer thinner some heavy duty steel wool and go to town. Tape everything up you don't want the stripper to contact. IT WILL EAT UP gaskets, rubber, felt etc. etc. I usually leave a half inch overlap between gaskets,felt etc. and the paint. Double it up as well. Then just go over it with 80 grit after stipping it. You will probably have to go over the areas a couple of times since there is more than one coat. The steel wool and lacquer thinner work well in getting all the stubborn places the paint doesn't want to come off. The thinner also works well in neutralizing the stripper. I would then DA the entire truck with 80 grit paper and rewash it with thinner and grease and wax remover before priming it with an epoxy type primer. Hope this helps some.
Oh yeah, I'm still planning on buying your jump seats if you still have them.
~Brian