R44 is discontinued, however NOS can be found online

R45 can be ordered, AutoZone will order if they don't have in stock.


The recomendation is city driving to the local coffee shop use the 45 heat range, if working the truck hard use the 43 range.
I've attached a photo from the 58 factory manual......
Attachments
Plugs.jpg (73.39 KB, 71 downloads)


1958 3100 Fleetside w/235 4spd