I recently bought a 1979 280zx and its havin a few problems with the engine, where the exhaust pours out smoke like its nothing. The engine has about 185000 miles on it and im planning to rebuild it. How much would i probably be having to pay to get the engine rebuilt?

I just reassembled an L26 for a friend.  It was $1850 CAD here in NS:

 

Edited March 29, 20197 yr by 240260280

So adding labor into that and praying that the issue with the engine is minor, a shop could rebuild it for around 3k?

Yes.... why not check with the local Z club. They may have some members who do the same work.  You would get a better quality job done and the price is usually fair.

http://www.nnzcc.com/

thanks a lot ill check em out and see how it goes

Unless you are worried about matching numbers, good used motors laying around for less than 1k. Those guys doing engine swaps about give away stock L28’s