Since our old friend GM Bulley is no longer here I guess I have to be the
voice of reason here.  Rick it is time to pull the old heads (or have them
pulled) inspect them, replace the gaskets (if the heads are still ok if not
then the heads with rebuilt ones from AVP) and put the puppy back together.
It is not that hard and it will save you from breaking down somewhere you
would rather not walk from or the engine going catastropic on you and the
$150-$500 (if you do the work yourself) head job becomes a $2000 (if you do
the work yourself) engine replacement.
Don't want to be mean but you were supposed to use the extra time that Moroso
bought you to save up for a proper fix.
Sorry but watching the temp gauge and carrying around gallons of antifreeze
are only options if you are driving the van to get the heads fixed somewhere.
Just want to save you money/time/hardship in the long run.
Ken Wilford
Van-Again
John 3:16