I like my Mossberg 500!
I like my 500 which I replaced the safety button with metal and removed the pistol grip and installed an adjustible Choate shoulder stock.
An orange follower that will not allow you to compress the spring too far along with a new magazine (tube) spring that cannot go BOING may also be what you might want. The orange follower is an easy way to quickly see if there are any shells in the magazine.
Other than my shoulder stock, I really didn't have to install the other parts.
I quickly found with 3" Magnum Buckshot that I'm not strong enough to keep the gun from nearly knocking out my teeth and/or breaking my jaw! Let's put it this way, when I ended up with a bruised jaw, I knew it was time for either 2 1/2" shells or a shoulder stock. I went with the Choate shoulder stock that comes with spacers to change the length of pull about 1 1/4" or so. I left the front Pachmayr rubber grip on -- which I find to be a good combination, along with the shoulder stock.
I basically made it just the way I want it and have not had any problems with it whatsoever. One good thing is you can buy parts for it all over the internet.
It's ready for defense if I should need it. I certainly wouldn't want to be the bad guy.