I have been looking for an acceptable substitute to replace the heater hose
which travels from the passenger side cylinder head to the front of the bus.
One end of the hose is 1" id and the other is 5/8"id. I could find no off the
shelf reducer readily available.  On the way home from work this afternoon, I
stopped at the local HWI hardware store to look for a way to make a reducer to
connect the 1" and 5/8" hoses.  I found a way to make a reducer for about 5
dollars.  I bought two barbed hose connectors.  One has a 1" fitting for a
hose and standard 1" pipe threads on the other.  The second has a 5/8" fitting
for a hose on one end and 1/2" standard pipe threads on the other.  To join
the two I am using a 1"x 1/2" reducing coupling.  These are all available in
galvanized pipe which should resist corrosion, allow the use of standard
heater hose (which reduces the price of future repairs), and should resist
extremes of temperature better than plastic pipe fittings.  I will be
replacing the affected parts this weekend.

Here are the HWI stock #s:

425114-5/8" hose fitting
425132-1" hose fitting
422150-1"x1/2" reducing coupling.

Rico
84GL