TIRES 97 = 8.85 x15 white walls 4-4 ply steel belted
926 = Scheduled Production date. Not all cars were actually built on the date listed.
N/7= possibly rear defroster. Does the car have one?
b/5 = coding quirk. Most online decoders, incorrectly, list this as code 565 rear arm rests. If that were true, then you would also see the code with bench seat cars. You do not. You see b/4 and b/5 appear with bucket seat interiors.
Tag codes, typically, relate to trim, paint and needing a hole punched in the body for some reason. (A/C, radios, tachometer, seats, console)
It appears the fold down arm rest was standard with M6W in the 68 300. It is likely the b/5 relates to code 485 FOLDING ARMREST. Does his car have the folding seat?
On line decoders = trust but verify. Most have errors and omissions.
j/0 = possibly 510 CORNERING LIGHTS. Does this car have them?