welcome to the site. some pics would be helpful. You can buy floor pans from ebay and weld them in easily. Painting them black or undercoat is good b/c they are made of cheap steel and rust readily. You can also buy higher quality floor pans from vendors like gbodyparts.com or 'goodmark'. If you want help posting pics is usually a good way to get started. Posting in this section won't get you far, so make yourself known in the buick section with pics. A member on the site is working to remanufacture doors but until then it has usually been standard practice to start with a 'new' used door which is not as rusty from a parts yard. This is usually more cost effective than doing battle with coagulated rust and blotches of rust converter / fiberglass and sheetmetal and all that. People have done patch repairs to door bottoms but if the rust is too bad it is standard practice to just scrap the door and start with a better copy, since you would have to strip a door down to paint it anyway this is much faster. hope this helps. +++++