I've never actually run anything except a stock fresh air "Deluxe heater" . Still for the guy who isn't doing a 100% original show room stock truck it doesn't really make much finanical sense to rebuild one and change it to 12 volt when other and probably better options are out there for far less money.
Lets examine the cost of rebuilding one like the ones I have out in the shed.
Heater core. one of the few that is rated for over 15 lbs right now is the one from Jim Carter.
https://oldchevytrucks.com/meh246.html Current inflation price on that one is 255.00 That is up from 170 something a few months ago.
12 Volt motor
https://oldchevytrucks.com/el116.html
That one is a somewhat reasonable 59.95.
Heater control valve
https://oldchevytrucks.com/reme202.html They almost always have some issue and need repaired or replaced
214.00 at Jim carter if they still redo your core if you have a rebuildable core or 155.00 if the price holds to rebuild yours at the Filling Station
https://store.fillingstation.com/det...E_REBUILD.html
The proper silver-brown heater paint from Jim carter
https://oldchevytrucks.com/pt137s.html
17.95
If you have a 47/52 the proper heater emblem for Chevy or GMC
https://oldchevytrucks.com/catalogse...+Heater+emblem
24.50
Lets see now
heater core---------- 255.00
12 V heater motot-----59.95
heater control valve -214.00
Paint -------------------17.95
Decal-------------------24.50
_______________________
Total ------------------571.40
Potentially 571.40 to correctly restore and convert a deluxe heater to 12 volt and install it and the control valve.
That doesn't count buying a heater if you don't have one nor rounding up a core for the control valve. Nor does it count buying a new blower switch and the control pieces for the control valve.
That is just something to think about if you are building one of these trucks as a hot rod truck and not restoring it to show point original.