So, I bought this truck a few months ago and I'm not sure what I should do with it next. I don't have a history of what has been done to it. I'm the 3rd owner, and the previous two guys had it for about 10 years each. I'll list what I know, and maybe you can suggest other things I should consider doing to it. I'd really appreciate it. This is my main vehicle now, and I want to make sure I do everything I can to help it last. It has 138k miles and the truck specs are in my signature.

Things I've done:

New front calipers and pads
New spark plugs, wires, distributor cap and rotor
Oil change
New brake master cylinder and power booster
New set of Goodyear tires
New battery

Radiator cap looked brand new when I bought the truck and the fluid looks clean, so I assume it has been serviced. I didn't flush radiator.


My concerns:
Do I need to flush the differential? Should I change the trans fluid? How much life should I expect on my clutch if this one has 138k miles on it, which I think it does?
Anything else that I should be looking at? I just want this truck to be reliable and mechanically sound. The engine sounds good, no misfire. I figure that I can fix almost anything else, so here we are. It seems to be in really good shape tho. Also, this truck sat in the driveway for about 3 years before I bought it. The guy started it now and then, but it just sat there. IDK if that matters.
Thanks everyone!