mounting bucket seats

I have a set of buckets I want to put in my 63 dart but the mounting holes don't line up by a long shot. My plans are to weld 1/8" by 3 1/2 fender washers to the inside and outside of the floor pans for reinforcement and go from there. Is this a safe way to mount the seats or should I try to make a frame that will use the old mounting locations?