Where can I get a water pump housing for a 1987 Dodge Dakota, A junk yard?
Besides finding one at a junk yard you could try a Dodge dealer too. Your generation Dakota was made by Dodge until 1996 and if your '87 Dakota has an engine that happens to share a compatible water pump housing design with any '96 model's pump design then you might have some luck. Manufacturers must make replacement parts for their vehicles for 15 years after the model is released - meaning the 1996 Dakota parts should still be available at Dodge dealers. Good luck.
You should probably try a salvage yard. They might have it, of course it probably wont be new....
Not sure what you mean by housing. Nobody is going to have just the housing. The entire Water Pump is available from Autozone, from $22 - $63 depending on type and warranty. The severe duty and new pumps are special order/available to ship. The standard reman is available in store, at my local store at least. Same pump as the 5.2L and 5.9L V8's. Can't be that hard to find. This is assuming of course, you have the 3.9L?