You will need to remove the entire floor pan. As you have discovered, the access hole is only large enough to connect/disconnect cables or top off the H2O, not big enough to remove or replace the battery. From my collection of trucks I can see an evolution regarding access to the battery. My '37 has no access at all, other than removing the floor pan. My '42 should be the same as your '45 with limited access. My '51 has the rectangular latching cover that allows you decent access so that you don't have to remove the floor pan. My '50 COE has that same cover as the '51, but because it is a cabover and the battery is mounted to the frame, that cover is under the seat. The COE adds a hinged door in the passenger side floor pan, so that you can access the right side of the engine. This allows you to check the oil, and do a tune up (with difficulty). Access is not a strong feature of our trucks.
P.S. To remove the floor pan, learn how to remove the floor shifter, then place the emergency brake handle vertically or slightly to the rear. These steps will allow the floor pan to clear the underside of the dash.
P.S. For the purposes of accuracy, I am adding this post script to correct something I wrote in the above original post. Looking again at my '37, it has the narrow limited access for the battery, identical to my '42.
Kent
Last edited by Lightholder's Dad; 04/27/2021 9:04 PM.
