<VV> How safe is it to drive w/ bad pinion bearings

[Daniel Goldberg]

Apparently my '65 Corsa has bad differential pinion bearings which, when the car is under load, causes it to behave as if it were driving over railroad ties.  

Swapping out the differential in my condo complex parking lot will be inconvenient at best.  I can take it to one of two locations to perform the swap -- one is 10 miles from my home, the other is 30.  Getting to either location requires traveling at highway speeds.

Will anything horrible happen if I drive either of these distances, or should I do the most risk averse thing and perform the swap in my parking lot?

daniel