Temperature questions

I have a '97 honda Passport 3.2 v6. I was wondering what the normal running temp for the temp. guage was. Mine hovers between 1/3 and 1/2 way up the gauge. I also notice alot of bubbling from the overflow tank whenever i shut off the car (after reaching full temp) Is that a normal thing? I had the radiator flushed and it ran cooler for a bit, but overheats if driven for a long period of time (over four hours, in the mountains at high speeds)Is there a way to make sure the radiator is clean? Should i try another flush or just buy a new radiator

try the thermostat first cheaper easier to install and very important

try the thermostat first cheaper easier to install and very important
That was the first thing i checked.
When i run the car with the radiator cap off it will bubble up a little (every 25-30 seconds one bubble) I have seen on other posts that this could mean a bad head gasket. this is something that the guys on this post have told me about this car from other posts i have written, but i guess i was just in denial about it.