I have recently purchased an '88 4/4. I suspect the tyres are the originals. (DOT code is 427) with less than 20k miles on them they are far from worn, but I suspect the compound is not at its best.
If there's no little triangle after those numbers then the tyres were made in the 42nd week of 1987 (if there is then they were made in the 42nd week of 1997). Either way you would be well advised to change the tyres.
As to make and type, it really depends what you want from your tyres and what kind of driving you like - but
anything will give you better and safer handling than those.
As Easter says, the aspect ratio in older radials is assumed to be 80 when not stated.
