I keep meaning to replace my gas heater exhaust pipe, just using the appro-
priate L of exhaust pipe from the FLAPS.  I don't expect a big difference 
in stinkiness, tho': a few inches difference in the position/direction of
gas heat exhaust is not going to alter the small amount that is drawn into
the clean-air intake, which is at the right side of the engine compartment.
If the gas heater stinks (and mine does, to a degree), I believe it is more
likely to be maladjustment, or oil film in the heaterboxes as was mentioned
in a previous post.  Probably exascerbated by higher volume and temp of air
flow when the gas heater is on.  Unless you have the only leakfree aircooled
engine I've ever known, you have some oil in your heater boxes.

First step in all these heater issues is to make sure the system is in good
condition and well sealed.  For instance, if the heater valves (flapper boxes)
are in bad shape, or unattached, or not adjusted so they open all the way, or
adjusted right but NOT opened all the way, then the gas heater blower will
pull in air from under the car.  In that circumstance I would agree that the
lack of a gas heater exhaust pipe might be an issue, since the gas heater
with no exhaust pipe points right at the left side flapper box.

B.