Nappa has it. Mine is the same 4.0 automatic 1988. Part number CSS980SB. It cost me $34.13, but I lie and say I work at a shop. Regular price said, $47.23. It helped a little but not much. If the truck sits for more than a day it still takes a couple tries and a longer crank to start. Everyone seems to say on this board that it is completely normal for this engine and year, so I wouldn't worry about it.