OK, so for a point of reference, here's my driver side floor (front seats and carpet removed). You can see that the anchor point is pretty much right around 6" behind the backside of the seat platform.
The new floor pans have the same metal formation.
When you weld them in, either cut around the anchor point and leave it in-place (like I did - that area was still good), or you'll have to "wing it" by drilling new holes and install the new backing plates Don (OMS) mentioned.
One other piece of advice: don't forget to punch the holes in the new floor pan sheet metal
before laying down sound deadener - otherwise, you'll need to get under the car, find the anchor points, carefully drill some pilot holes, remove some of the sound deadener, and drill the new holes - all without mucking up the threads in the anchor plats. Ask me how I know this? :whistling:
No locating dimples, no holes, "no nothing," yet:
Still hadn't punched the new holes:
... And here we go with the RAAMMat - the holes still aren't there... trust me.
I even went the extra step and actually finished the interior... still no seat belts (because there STILL were no holes):
Insert "facepalm" smiley here.