Those batteries should do just fine.
I'm running what are basically identical batteries, but NorthStar branded (same case, same posts, just a little different specs) for almost 4 years now and they are great.
Yes, your truck is an M998, or possibly an M998A1, but definitely not an A2 or newer version. That 2004 date on it would be the last time it was rebuilt, not when it was manufactured. There is a thread on here that gives approximate build year by serial number, but that will also depend on them not having assigned it a different serial (uncommon to change serial unless it went through a recap program like the M1097R1s did)
It's recommended you only buy parts like glow plugs through reputable venders, not ebay. Too many chinese knock offs on there, and not worth the money.
As for business and towing trailers, you'll want a real 2" receiver like the one from Black Dog or Federal Military Parts, not one of the pinball type that bolts under the pintle. You might also need a trailer brake controller if any of your trailers are over 3k lbs. You'll also need to either get a trailer light converter box, or put all 12-24V leds in your trailer sockets for them to work and not blow.
Thread on trailer brake controller install. I went with the Federal 2" receiver, XM381 converter box, and Red Arc trailer brake controller (will take 24V in and do 12V out to brakes)
A couple days back I installed the Federal Military Parts class 3 heavy duty 2" receiver I picked up from another member here who decided to go a different route. Doesn't work with airlift bumper, which is fine with me, as I don't have one. Got it installed and was waiting on the other parts...
www.steelsoldiers.com
Here is a picture of my batteries installed (24AGM) Cables all reach just fine, and works perfectly with original hold down bracket.
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