Re: Question about my 540S Saber
Well, one way I believe to check the body is the pickup switches. I think the 87 and 88 models had mini-toggles for each pickup but they started using 5 ways in 1989. So, while the neck is definitely and 89, the body may be an 88.
That being said, other than general curiosity or some "all original" value (whatever that may mean), I'm curious why this would be an issue. I've swapped necks on literally dozens of older Japanese Ibanez guitars over the years sometimes out of necessity and sometimes because I wanted that reversed neck on my 540P Tiple Coil instead of the DY Saber it came on. And a lot of people obviously are always parting those guitars out on the auction site we dare not mention, plus a lot of those older necks crack and warp over time so they made need to be replaced, but you still have a nice Japanese neck made in the exact same factory by likely the same workers, so the quality is the same. There's no magic when they put the neck on at the factory, and the Japanese are pretty well known for keep standards tight, so the necks are generally easily interchangeable.