Before a long trip, what truck maintance things need to be completed?
Obvious things I am planning to take care of:
New tires, tire pressures,
spark plugs, oil filter, air filter, serpentine belt.
What else need to be looked at?

 

top off with oil and monitor as needed. my niece just blew up an engine while traveling and not checking.

coolant, battery, battery cables, windshield wipers, wiper fluid, check all lights including high beams. take a flashlight and in your cold climate - a sleeping bag in case you need to not freeze to death.

if you have any leaks at transmission or rear end, check those fluids.

check that its tracking straight while going down the road - let go of the wheel to see if it stays in road or pulls to one side. if it pulls get an alignment.

 

If you are putting on new tires, I would do an alignment along with the tire install. Alignment doesn't have to be off much to cause increased wear on a long road trip.
As to tires, do not forget to check the spare for age and inflation.
While the tires are off check the brake discs and shoes for wear.
Check heater output and A/C also as it runs with the defroster to dry out the air.
PS level check.
If you have any lube points in the steering hit those.

Not truck related:
For emergencies I usually carry an emergency blanket, just in case you come across another accident. I also carry flares and chemical glow sticks. Traveling this time of year it is smart to carry snacks such as nuts and fruit/energy bars in case you get stuck in a surprise snow storm. Water too.
I usually do not let the fuel drop below 1/2 tank. Got stuck on the Iowa/SD border one time for 18 hours as the freeway was shut down. No room at the inn and no fuel at the stations. Good to always have some in reserve.
If you are traveling any passes, get some chains if you don't have any. I also carry a 10,000 lbs rated tow strap.

 

As far as prep goes, it seems you have the major things covered.
All I know is I tend to carry the kitchen sink with me. It especially started once I put in a tool box in the bed haha.
I'd suggest at least taking an extra quart of oil and tranny fluid, a gallon of antifreeze (either premixed or get concentrated and make two gallons!), a tow strap/chain, jumper cables, and hell, maybe even a couple of spare light bulbs.

 

And a spare serpentine belt. Not to mention the tools required to change any parts you happen to bring with you.

I would go for a gallon of oil....

 

and get you a real jack not one of the POS scissor jacks are trucks come with will make life so much easier if you have a flat or something.

 

2nd gens came with bottle jacks I believe, and they work pretty good in my opinion especially for solid axles. But maybe he doesn't have it still!

 

Be sure to drink your Ovaltine.

 

Thanks for all the great suggestions..

Had to replace the speed sensor over the differential to clear an engine code. That was simple enough but I moved a brake line that runs over the differential. A few minutes later sure enough there was a puddle of brake fluid developing on the driveway by the left drum. great.
Had a hard time getting the proper thread to match with a new 60" line set. Snow is flying and I'm curled up under the back of the truck. The thread was right pitch but the new adapters were 9.8mm diameter vs. 9.3mm for the old ones. They just wouldn't thread in. I ended up using the old adapters and making a new line. Has anyone experienced that before. Maybe they gave me the wrong size at the Parts Source.

 

I like to have a CB radio in any vehicle I'm taking a long trip in. Closer to cities you have allot of idiots that like to be annoying on channel 19 but get out on the long stretches of highway and there's still allot of drivers sharing helpful info.it's a great way to get a heads up on road conditions and accidents, plus there's still a few rural areas that monitor channel 9 for emergencies. I see your location is Ontario , many of the Canadian drivers i ran with used 10 or 13 for the general information channel.