look at this picture of original parts, gas tank doesn't look painted to me .... and not unusual for a California truck to not have a heater

if your floor was blue under the tank, it's not original, floors were dark [charcoal] gray - and if the back cab wall was painted interior color, it indicates the interior was painted before the tank was installed, it wasn't "part" of anything - the tanks were installed when the truck was being assembled, well after any painting on the cab, and as identical tanks went into all different models for 5 different years, with different interior colors, they were the "natural" grayish galvanize color

Bill


Moved over to the Passing Lane

"When we tug a single thing in nature, we find it attached to the rest of the world" ~ John Muir
"When we tug a single thing on an old truck, we find it falls off" ~ me
Some TF series details & TF heater pics