Here is a link to my pan replacement,
http://forums.pelicanparts.com/porsche-911-technical-forum/963780-first-post-partial-front-suspension-pan-replacement.html
Relative to the internal finishing, I used a weldable primer, prior to assembling the parts. Of course I do not buy that it flows and seals everything off during the welding process. After assembly, I used and internal frame coating from Eastwood that was injected in heavily until it ran out the seams. I then applied externally epoxy primer followed by seam sealer. UPOL was installed to match the factory coating before it was top coated. Oh, I did also inject Fluid Film in the cavity also.
Jeff