Hey CS,
I cannot speak for the Model 87, but I can definately speak for the newer Model 37s they are making again. I got my 12 GA Ithaca Model 37 in November 1996 directly from the Ithaca company, and it included three chokes which fit completely inside the barrel. Getting other Ithaca chokes was not a realistic option for me, and the lady at Ithaca told me I could use Winchester 12 GA chokes. I bought a few Winchester chokes, and they work quite well.
About 3/8ths of an inch of forward end of the Winchester chokes is knurled and protrudes from the end of the barrel. Some folks may find objection with the looks of the Winchester chokes sticking out of the end of the barrel. For me it is not a problem. In fact, I prefer the Winchester chokes because they are easier for me to change than the original Ithaca chokes that are hidden inside the barrel. When shooting sporting clays, I simply use thumb pressure to tighten and loosen the Winchester chokes.
Hope this helps.
Best wishes,
Dave Wile