Ended up just slapping the third in. Karl214 and I got it done after a full day of BSing, fighting rust and crust, and generally trying to fit large hands in spaces that tiny hands would have been better.
It's sitting on stands in the garage right now so the RTV can dry. Tomorrow all I should have to do is fill the rear diff, bolt up the driveshaft, put the tires on, and then go see how much faster I can conquer some of the local 55mph hills.
Thanks Karl!