Ron Pattinson has dug up plenty of IPA recipes over the years, both
on his blog and if you poke around Google Books - it's always courteous to buy a book if you're using the recipe though.
Although the weight of hops seems large, you have to remember that this would have been before the days of cold chains and protective atmospheres/mylar vacuum packs, so you have to wonder a bit as to what state the hops were in. In air at room temperature, the half life of alpha acids in hops can be less than six months.
Also you have to consider what varieties were being used - for instance Tolhurst was widespread in Mid Kent between the wars, and I've seen that analysed at just 2.2% alpha, it was definitely the "cheap and cheerful" hop with great yields of not so good hops (as well as a notoriously poor keeper). One would hope that as premium beers IPAs would get the premium hops like EKG, but when have big brewers ever taken the more expensive option....?
In terms of commercial beers - all the "original" ones have suffered through the 20th century and are now a pale shadow of what they were, your best bet are the breweries that make heritage recipes, such as the guys at the Burton museum and Beer Nouveau (who even made the infamous
cock ale for IndyMan this year).