His was a '78 for sure K30 chassis. literally ideantical to that one. I've been in it a bunch, its pretty big inside. and the mileage IIRC was 8 or 9 mpg. every day all day. thats what my '86 K30 crewcab SRW used to get with the 454. maybe 10 mpg unloaded. it is what it is.
I've been trying to find pics of his old pig. but it sold like 4 years ago when the 5'er and D-max came on board.