I’ve welded new pans into my 68 442 and am looking for diagrams or measurements on where to tack the new bucket seat brackets in place on the new pans. Thanks!

 

No measurements but some pretty good original pics:

 

Not sure if you are still looking for this info, but the best way to place the brackets is to use the outer rear mount in the floor as the "fixed" point. Bucket and bench seat cars both use that mounting point. The only difference is that bucket seat cars only used the outer bolt hole not both. With the outer rear mounting point bolted down, put the inner and front outer weld-in mounts under the tracks and move the seats around until they are square in the car.