What to ask for Core 1985'ish 727

When selling, you should specify if it's a "lock-up" or "non lock-up". The converter end will have splines all the way to the tip if it's for a conventional "non lock-up" converter. A "lock-up" will have about a 3/4" smooth tip. Lock-ups started around the late '70's and converters will not interchange with conventional transmissions. It can be converted with the proper work/parts, including valve body & pump. .