I replaced the front stuts on my 1996 Lumina - it's exactly the same set up as the Monte. Here's a picture of the parts I installed. I had no problem dropping the new strut into the shock tower. There is no "end cap" on these struts. There should not be anything at the bottom of the shock tower to obstruct the installation. If there's something down there, maybe it's a part or piece that dropped in by accident???

Below - strut. Smooth end goes in first - on bottom. The large nut goes on top - holds the strut in place. Then the top plate (not shown) goes over the whole assembly. Finally the small nut goes on after the top plate is installed. There are other parts involved - rubber bounce stop, strut plate isolator, rubber boot, etc. - all reusable assuming no damage. They are not pictured.

 

All the weight should be on the wheels. It should not be raised up. Just throwing out anything here.