[geezer#99]

You got your math wrong.
You don’t add the spacer width to your backspace, you subtract it.
Your originals at 3.5 bs with 2 inch spacer gives you a 1.5 bs.
Your intended new wheels with 4.5 bs and 2 inch spacer give you a 2.5 inch back space.
The wheel/tire will stick out further and interfere with the fender lips.
You need a rim with at least 6.5 inch back space.