I think you do not have the whole stuff then...

"WWIIaircraftperformance", without the "spitfireperformance" part is 2.55Gig's on my drive.
At the moment, my "spitfireperformance" rebuild is 48Meg's and it's only the MK1 page with a sublink to the page "camparaison spit vs 109" included, but this one is not finished yet, there are more than 330 links on that page, crazy work to check them all ,a lot of links point to the same docs used on the mk1 page, but not all, so always need to check if the document already exist, otherwise download it from webarchive, adapt link to fit local html architecure (in all cases anyway), check link locally...
Otherwise, there is a possibility to get the PDF's on the webarchive, but you need to scroll through all the "records" of the page that have been saved on the webarchive, with little luck you'll find it somewhere. (or try using the direct link to the file , right click, copy link, paste in webarchive)
If the original webpage doesn't come back online within 2or 3 months, when i finished the "spitfireperformance" part of the website, i'll post it as back up.
Otherwise, do the modo's have Mr Mike Williams' email? if possible to check with him what's going on?