I have doubts if a vacuum reservoir can would work on long trips at highway speeds. Those cans are likely for providing a buffer for fluctuations in vacuum delivery rather than providing a reserve of vacuum.
I would like to hear from someone who has used a reservoir on a 216 or 235 and have evidence that the can solved their wiper woes on extended highway speeds.

1952 5-window - return to "as built" condition | 1950 3100 with a 235 and a T-5 transmission