LJ, that's not going to work.
1) 5x4.5 has a bolt circle (center to center) of 114.3mm. The center bore (hub size) on the 100 is 110mm. Take your front and rear center caps off and examine it a bit with a ruler. This may help you understand what I'm saying. A jeep owner could use 100 series wheels with an adapter but not the other way around.
2) Most 5x4.5 wheels are near zero offset. Add any size spacer and you'll be in the negative offset arena. Say it was a zero offset, 8" wide wheel, or 4.5" backspacing. Add 1" spacer and you'll be down to 3.5" backspacing.
The 100 uses +60mm offset wheels (8") width. This is almost 7" of backspacing.
Which wheel style do you want?