150K maintenance question

My 2001 GMC Sonoma 4.3L just hit 150,000 miles and I was going to do some work just to keep it running well. I already do the brakes, oil, air filter, cleaning MAF & throttle body at regular intervals.

Things I’m planning on doing:

• Spark plugs + spark plug wires
• Fuel filter
• Thermostat (probably an entire coolant flush because it looks funky with lots of rust)

My question is what else should I look at/do that isn’t normally done?

The truck runs great, I just want to stay on top of things to make it last as long as possible. Any help would be appreciated!