I think the upper floorboard is removed to access the throttle assembly. There are several different springs(5 assemblies, I believe) installed with the assembly probably out of the car. Two bolts fasten the throttle assembly to the bell housing. There are two places on the top side of the assembly for oiling, to keep the throttle cross shaft happy. Check for alignment. With an engine replacement, the throttle assembly can get bumped, mangled, and misaligned.