Originally there were three part nos used on the '60 model rear shocks:
5552329 LeSabre/Invicta (less wagons) standard duty
5552330 LeSabre/Invicta (less wagons) heavy duty
Electra/Electra 225 standard duty
5552332 LeSabre/Invicta wagons
Electra/Electra 225 heavy duty
By '72 only the 5552332 was available at the dealerships and was specified for all '60 models. With all this interchangeability on the originals, the MA700s should work in your car.
Another supplier (Gabriel) shows a standard replacement shock no 82155 as fitting all series of the '60 Buick.
Monroe also specifies the MA 700s for use on some Cadillac limousines which weigh a lot more than the Buicks.
The Monroe website omits a lot of Buick series of the early 60s in their parts selector. My guess is their research Dept quit too soon on the senior series cars. This looks like a good question for their tech talk response function. Maybe they can use the OEM part nos to confirm the applications for all 1960 Buicks.
What has been, can be again. (Bob Wills, 1942)