Looks like a good trade. Was it a new lower? Because it doesn't look like it has any finish wear on the top of the buffer tube threaded hole, or where the upper receiver would touch the lower. Get yourself: a complete upper; complete stock of your choice(stock, buffer tube, spring and buffer); a rear take down pin,detent and spring; buffer retainer and spring. It may be cheaper to buy a kit and then sell the parts you don't use.