USMC6282 has posted photos of his Remington 870 with Magpul upgrades on Remington 870 forum:

So a few weeks ago i purchased an old remmington 870. looked up the serial and found that it is older than i am. it’s a 1979 wingmaster with the barrel cut to 18.5″. when i first recieved it the safety was stuck in the off position, and it was a little (really dirty in my standards) condition. upon coming home i tore it all apart and found cosmoline on the bolt and trigger group. its weird because i figured the previous owner would have cared for it. so did a full inspection, complete cleaning, repaired the safety, and put it all back together. then i didnt like how the worn bluing looked so started to sand the reciever and finally decided to hand polish it starting at 80 grit and progressing to 3000 grit wet/dry and finally polishing paste. then i noticed the stock was cracked in multiple spots so that had to go. all in all i purchased the gun for 200 dollars and put 250 into it.