I realized I goofed in my post. I bought the 80% lower from American Made Tactical but the lower kit from Ground Zero Precision. More than half of the lower kit GZP sent doesn't fit the AMT lower. I'm having to buy springs, take down pins etc separately. Even the Elftmann drop in trigger didn't fit. I bought a Geissele SSA-E and it fit perfectly.
Thanks for the response, Survivalshop. I contacted Brownells last night and they have the spring I need. For those of you running into the same issue, they sell a dpms detent spring with a diameter of .090" and is 1.090" long (item #231-000-094). This should fit since its only 3 thousands larger than my takedown pin detent.