ok. I have this tank: Its a 31 gal. tank out of a blazer but I dont know what year. I fabbed this tank into the back of a Scout and am in need of a fuel sending unit. Ive been looking at my catelogs and have found several different sending units. Some have 3, some have 4 ports and they have different senders for different year blazers. What are the differences in the units? Can I pick any sending unit and put it in this tank if its for a 31 gal tank? I noticed that pre 78 units are about 80 new and after 78 they are about 160 new. in 87 they go up to 330 because of the intank pump. I will have no clearence problems above this tank and plenty of room for any port combonation. Will any sender fit into the top of this tank? I already bought the lockring and it says it works from 73-91 so that should mean that all they 31 gallon fuel sending units should work, the differences is the port configuration. Can somebody confirm this before I spend 80 on the wrong sender then turn around and have to spend 160?