On the one hand that starter is pretty old. On the other hand, in my experience if the starter is bad then it doesn't do anything. It sounds to me like a voltage drop somewhere which are very common, especially at the battery clamps, also where the clamps connect to the cable, also ground connections. I am just saying consider that when you put in the new starter it might not fix the problem. I have had that experience before.

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1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra