I have done this twice recently. I bought from a gunsmith all the parts needed inlcuding the stock for $85. the stock was $20 and the bottom metal including spring and follower $65. when they do builds generally the stock is not used and if a guy is building a gun with a detach mag, he isnt using the bottom metal. not sure if the spring and follewer are different, but for cheaper than new you could get both anyway. good luck