I run a long bolt through one of the threaded holes and place the threaded end in the hole in the floor from inside the cab so that I can use it to line up the hole for the first bolt coming in from the bottom. I snug that one down tight, remove the "alignment" bolt, then install the remaining bolt from the bottom.
Carl

1952 5-window - return to "as built" condition | 1950 3100 with a 235 and a T-5 transmission