>> But just in the past week, I've been noticing my temp gauge going
>>past the half way point to about 3/4.

I don't think this is normal, especially if it's going up fast.  First,
bleed your system as per Bently. Next, after your vans has been sitting all
night and was run up hot the day before, open the coolant tank (not the
overflow) and fill to the top if there is air in there.  Do this again the
next day and so on until there is no more air in the tank.  This will
squeeze out the last of the air in the system.  My temp gauge NEVER goes a
hair above the led because of this. Before I bled it correctly it used to
go to 3/4.  I am convinced many Vanagons out there are not flushed
completely of air and this is a contributing factor to their head problems.

Bryan