I decided to upgraded my old 590. Typically this is not a HD gun for me but My 3 gun shotgun.

I've ordered a choate 3 shot tube extension for it and it typically wears a buttstock cartridge carrier and a sling(carry strap).

I'm thinking about switching the cartridge carrier out for a speed feed buttstock and replacing the current forend with an old (used) surefire weapon light forend.


Other than the usual suspects (ARF EE, EBay, Gunbroker, arms list, GunsAmerica) where can I find parts?

Is there real value to the speed feed stock? Are there substantial training issues to master? Are there wear parts I need to examine/replace?

Where should I go for a replacement light for the surefire? Any model suggestions?

I just got a 590, so bump for the info

I'm a little confused, are you turning your 590 into a HD or a 3 gun setup?
I think you are going for HD, so my recommendations:
Mesa Tactical; stock adapters/ammo carriers/rail mounts
Magpul for furniture. Their forends allow for rail and light mounts
Esstac shotgun cards at SKD tactical are another great option for extra ammo carry
GG&G followers
Aridus Industries ammo carriers, expensive but also innovative

Thanks Ch45x7,
My theory on 3 gun is: I'm never gonna be Jerry Miculek or Todd Jarrett. So, I try to keep my guns the same as HD guns. My pistol is the Glock I carry. My rifle is a pretty basic M4 knock off and my shotguns are basic pumps. While I don't use the shotguns for HD, I like to keep them set up as HD guns. I figure familiarity with a solid defensive setup can't be bad.

Look into having your barrel threaded for choke tubes and the forcing cone lengthened.

Also forget the speed feed stock and get a side saddle. I have both on my 500, but the side saddle is far more useful, the speed feed is more if for some reason, I need more than 11 shots.,  I mainly got the speedfeed because the FFL had a used one on the shelf and it has a shorter LOP than a standard 500 stock.

GG&G Follower is a Great Upgrade
VangComp Safety is another Fantastic Upgrade,  It's BIG and POSITIVE
ESSTAC Shot Cards from SKD are Wonderful, get Many!

Magpul stock and surefire forend with Malkoff LED.
Choate mag extension.
Sidesaddle ammo carrier.

My .02 cents:

Ditch the Speedfeed stock and the side saddle. Get a SF fore end and put velcro on the receiver and use shell cards. Would consider replacing the bead sight (if you have this type) and add a good sling and call it a day.

Take a look at the Vang Comp + 2 extension. I have one one my 18.5" 590a1 and it sits flush with the barrel.  The also come with a Vang Comp follower and extra power spring.  

My 590a1 came withe the speed feed stock...I like it but like the previous post, I prefer having extra rounds in a velcro shell card on the side of the receiver.

Midwayusa had the choate +3 magazine tube extension for sale at $32. Installation was easy and test feeding indicates proper function. Unfortunately, it does poke out a little bit.

I overlooked that you already bought the Choate.  I really like the Vang Comp extensions...have one on my 930 tactical as well.  They cost more but they're high quality / very well made / one piece steel construction.

This, but I prefer a small rail up front for a light if I need one. The speedfeed is worthless, and try shooting it left handed. I also love the extended safety I added, worth every penny. Ghost ring sights, or get a top rail and MRDS. The receiver cards are what I went to, I actually removed all of my side saddles and went this route.