Any advice is appreciated. Just bought an 89 IROC with almost 100k miles on it. I don't know the service history. It has the 350 in it. Runs strong and easily passes smog. Supposedly has been sitting for years and smokes a little on start up. Other than new fluids, should I flush engine, gas tank...

 

full fluid change is a no brainer if you have no record of service . smoke on start up normally is valve seals . if it's just a small amount of smoke & passes smog , seals may be o.k. . remove valve covers and make sure drain holes at lwr. front and rear of cylinder heads are not sludged up . this can cause oil to drain slowly back to crankcase & build up in cylinder heads . also a can of eng. flush prior to the next couple of oil changes could not hurt . almost forgot , change fuel filter , fill up with fresh gas , should be good to go . good luck .

 

If you're going to keep it as a daily driver for years, I would change everything rubber on it. Hoses (coolant, vacuum, fuel), fanbelt, sparkplug wires.
If you see a 20 year old car on the side of the interstate with the hood up, it's always something RUBBER!