Posted for Mark Steitle <msteitle@mail.utexas.edu>:

Al,
Thanks for the info.  I had considered the plusses and minuses of having a big hole through the firewall necessary with a heat muff as compared to an H2O exchanger in the cowl.  I have a 65 Mustang heater core that fits real nice in a little niche inside the cabin, just aft of the firewall.  This location would make a neat and relatively easy installation.  Mustang heater cores are available and pretty cheap through the many Mustang parts vendors.  I'll do some more fitting and checking to see if I can make this work.  Is a blower really necessary with that big fan up front?  I was thinking of a little NACA scoop to feed fresh air to the heater core.  (Trying to keep things light).

Mark