Sam Jones (Skylight Inn BBQ, Sam Jones BBQ) out of eastern North Carolina recently put out a book all about whole hog cooking. In it he provides some good instructions and pics on how to build a cinder block pit for cooking a 200Lb hog. His dimensions are 5'4" wide and 8'10" long and 2'8" tall. (4 blocks wide, 6 blocks long, and 4 blocks tall).
I imagine a 4' x 8' pit would work pretty well for a 180Lb hog and it's it a bit tight you can always cut off the feet.
Good luck with your cook!
