Replace rear steps

OK the rear steps on my unit came to an unfortunate end out in Montana. Now back home I ordered and have here a set of replacement steps. Geez they are very heavy. The old steps seem to be welded in. At least I can detect no bolts.

The new ones came with no instructions and four bolt holes. This is a 24 inch 3 step unit (strom-carlson replacement).

Before I get the angle grinder out and cut the old set off, does anyone have any suggestions? I'm sure I'm not the first to go thru this.