Over the years I been told many different reasons.
01 The 87 don't have the frame support like the 88 and jumping the 87 can cause cracks.
02 Due to the more aggressive porting that is out now that can weaken around the ears
03 I would only do this if a bore is required are having a aggressive porting done, you will loose a bore  when welding ears due to warpage, your cylinder will also need to be decked from the bottom to be squared with top and you will be required to use a thicker base gasket when assembling to keep port timing correct.
If I missed any thing I sure SQ-HQ members will add more.