Where (on the internet) can I find a complete listing of specifications for my 1990 F150 XLT lariat, 302 standard cab? I would especially like to know the weight of the tailgate.

https://en.wikipedia.org/wiki/Ford_F-Series_eighth_generation

Pretty sure the weight of the tailgate is not listed in the specifications. Perhaps you could use a bathroom scale or similar and weigh it?

Thank you for your help Bob. Got the tailgate today....2 dents at the top...ugh! And looking / comparing with my original tailgate, new one looks thinner...is there a way to measure the "gauge" of the steel?

Here is your problem. I've been through this before. Neither Ford or any other manufacturer I know of makes body parts for vehicles once the basic model configuration has been changed has changed for a few years. Dealers do not stock these items as cost and storage space is a major consideration. OEM does not always mean metal gauge will be exactly the same or the compensation of the alloy will be exactly the same. My previous endeavor in an area similar to yours always brought me to a junk yard with a magnet. The magnet was used to determine how much bondo repair, if any, had been previously performed.

Go to LMC Trucks .com, and then order u a free catalog,it will give u all parts.