Sorry, Ken300D, I forgot to answer your question.

<<
Where is the block heater plug cap located?
>>

Mine was near the bottom of the grill but inside the grill. I had to open the hood to see it. I guess it can be pulled outside the grill. It is just a regular plug with a cap on it.

I heard that the 1987 diesel do not have this installed automatically but owners get a coupon in the delivery package to get a free block heater. So some owners may not have taken that offer in warm climate.