re the Stewart Warner gasoline heaters, and when/what AC used them
In the maintenance manuals the actual heaters under discussion are called Stewart Warner Hermetic Combustion heaters - from here on indicated by the acronym SWHC followed by the Model number and BTU output if available. The heaters themselves used a fuel-air mixture connection ported from the supercharger.
USAAF P-39C thru D-1 and UK P-400 used 1(?)x SWHC Model ? ? BTU unit. (I could not find the model number so I do not know any details.)
NOTE that the Soviet P-39 manuals mention the Stewart Warner heaters also, along with another type of combustion heater, plus electric heaters (in effect space heaters) adapted for the P-39.
USAAF A-36A-1 Apache/Mustang, P-51A-1&A-5 Mustang, and UK Mustang Mk I&IA, used 2x SWHC Model ? 10,000 BTU unit (with integral blower), 1x in each wing (just outboard of the guns) for heating of wing guns only. The gun heating system was switched to electric heaters starting with the P-51A-2/A-10 series and continued through all subsequent models. An air duct/tube system using warm air from behind the engine was used in all models from the first production airframe.
USAAF A-20C thru G-10 used 1x SWHC Model 791-D 40,000 BTU unit for cabin heating. 1x 8500 BTU unit was used to heat the guns in gun nose models.
USAAF A-20G-20 on used 2x SWHC Model 791-D 40,000 BTU units to heat the cabin, and electric heaters to heat the guns.
(UK Boston AC used the same heaters as the equivalent USAAF airframes.)
USAAF B-25C/D (early- to mid-war) equipped for cold weather used 2x units, 1x SWHC Model 790-C 80,000 BTU and 1x Model 791-D 40,000 BTU.
USAAF B-25H-5 and B-25J (late-war) equipped for cold weather used 3x SWHC Model 906-A 50,000 BTU units. (7" dia x 17.5" L)
(UK Mitchell AC used the same heaters as the equivalent USAAF airframes.)
USAAF B-24C thru H, PB4Yx, and UK Liberator II thru VI, used 6x SWHC Model 789-F and/or -G units (all of 8,500 BTU output with integral blowers). (NOTE: Some late models of B-24 had a ducted air system, which used the engine heat for warming the cabin and de-icing.)
Early production USN and RAF PBY-5A used 1x SWHC Model 792-A 80,000 BTU unit with its own dedicated 1.4 HP motor. It was used for heating the cabin, and could be used for warming up an engine before start if necessary. Late production PBY-5A used a Skyheat Combustion Heater Model SGE-1 90,000 BTU unit with its own dedicated 2 HP motor. The Skyheat unit was retrofitted to most surviving USN airframes. A 1x SWHC Model 901-A 100,000 BTU unit was used on most airframes as a dedicated de-icing heater for the tail empennage.
USN and RAF PBY-5 used 1x SWHC Model 782-N 80,000 BTU unit with its own dedicated 1.4 HP motor. It was used for heating the cabin, and could be used for warming up a cold engine before start if necessary. Some PBY-5 used the SWHC heater for the empennage.
NOTE that some PBY-5 and -5A were not fitted with the combustion heater systems, depending n the customer's order and intended area of operations.
I have found non-specific data for Stewart-Warner heaters used in aircraft up through the B-36 bomber, along with another type with the name including the word Norman.
NOTE that the above is what I found with a few hours searching.
Model 792-G 20,000 BTU unit weighed 27 lbs for the heater unit alone.
Model 940 20,000 BTU unit (immediate post-war, used by Piper) weighed 21 lbs for the heater unit alone.
The draw-thru blower motor weighed an additional 5 lbs according to the weight and loading charts. There would be 1x blower motor per heater. You would have to add the ducting and wiring/control box to get the overall installation weight.