Nice paint job. You should a step by step tutorial on how you did it including surface prep.
I vote 1187 do to recoil if for a kid (that's what I got for my kids). If for an adult I'd still do the 1187 just cause autos are cooler! Haha, I got 3 new 870's that i thought i was gonna let my kids use but the 1187 shoots so much softer that the 870 will most likely never be used. As far as shells, I opted for a 2.75" 1oz #6 heavy field load to cut recoil down to a minimum.