Battery Installation is Done
Thanks again everyone.
Installed the new house batteries yesterday with the help of my neighbors, one of whom has every mechanics tool ever invented.
The pair under the hood went smoothly. Not so with the pair under the chassis.
The stainless steel pins holding the tray had seized completely (looks like a galvanic reaction). Could not budge them. Had to unbolt one end from the chassis, cut the bracket on the other end and fabricate a plate to reattach it.
The job took three and a half hours. I'm really glad it's done and it should be easier next time.
If you have a setup like this, you might want to check the pins holding the tray so you can be prepared when the time comes to replace the batteries.