On May 29, 2012, at 9:09 AM, David Beierl wrote:

Replace it with a
Marshall - 290 I believe is the correct one, for horizontal mount -
someone will confirm.  It's about an inch longer, you'll have to
massage the connecting lines a bit or shorten them.

Yup. Be sure to order the one that vents down, rather than forward.
The one you want has a 90 degree-from-straight in-line vent.
THe wrong one tends to get clogged up with ice/slush sitting
where it does behind the front wheel. The 90 degree down
facing one, especially with the plastic protector on it, is not
exposed to this.
This is what and where (I got it) I put on mine recently:
http://busdepot.com/details.jsp?partnumber=253070604
You can see how that vent hole faces 90 degrees to the line
of the regulator.

bob