All original equipment batteries have a label listing the part number of the replacement battery. On the 1988 Regal, this label is on the battery itself, and may also be on the heat shield.
The AC Delco part number listed on early Regals, built approximately through mid-April, is incorrect because the "eye" is in the wrong location. Otherwise, the two batteries are identical.
The correct service replacement battery is:
75B - 72
General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.