The alnico Super 3's are out there, even though it may take a few days/weeks. Trust me when I say, you want to source a pair of originals. The Super 3 was Wharfedale's main tweeter back then (for the upper-level stuff) and was used on many different models, so you should be able to find a pair soon enough. It will be worth it, believe me. Those tweeters are ESSENTIAL to that classic Wharfedale sound. The alnico Super 3 was used in the SFB3, W3, W4, and Airedale, as well as the early W70 and W90 models, and it was their primary tweeter throughout the '50's. You want them, trust me on that. They will make all the difference in the world to those.... ESPECIALLY those, which have the tweeter facing upwards (The original Super 3 is great for either forwards or upwards-facing applications, and it is a WONDERFUL-sounding tweeter... Surely one of the best cone-tweeters ever made, and you do NOT want to substitute a cheap Japanese/Chinese tweeter in it's place... It's sacrilege).
By the way, nice going scoring a pair of TOTL'ers. Give those the proper attention, and I assure you, they will sound amazing. I have a pair of W90's from the same early '60's era, which share the same tweeters (The W90's have TWO Super 3's per cab... Somebody just scored a pair of W90's... Go read his listening impressions of them if you want to get an idea of the tonality of those Airedales).
Someday I'd like to find a pair of W4's, which are the next model down in that series. They're like the Airedale's younger brother (By the way, the modern reissue/interpretation of the Airedales are like $40,000 a pair... The originals cost as much as a downpayment on a very-nice house back in the early '60's).