A-518 Lockup and OD question

I have done a bit more research on the vacuum switches

PATC supplies Superior Products switch KO58 6 to 22 ins vacuum
Superior Transmission Parts offer KO52, 1 to 6 inches of vacuum for GM and KO58 for Chrysler, so it looks as though 6 to 22 is the required range.

By my calculations this equates to 3 to 10PSI or 20 to 75KPa so I guess if you are going for the Ebay switch the -70KPa is probably the one to go for.

I'm not an expert and haven't tried one of these switches yet so please don't rush to buy on my suggestion. I'm going to risk $22 on one for myself and will report back. I plan to measure the hysteresis - difference between on and off vacuum on both types of switch to see if one is likely to be better than the other regarding cycling on and off.