Just seeing this thread for the first time.
@Canuk are you still thinking of DIY? That's audacious — you could use it for Audax!
I'm certified in 753 but I only made two frames with it, made a similar number in 531SL which is almost as thin.
Ironically I wasn't certified yet when I made the frames I made, circa 1980, then got certified but didn't make any more after that. That's not the usual order, but I've always done things backwards.
You probably know, earlier sets were metric-sized only. So if that's yours, then your lugs need to be sized for metric too.
I still have maybe 3 sets of 753 road, old metric-sized and a set of off-road, not sure if I'll use them in this lifetime but I just like having 'em.
Do you know Kevin Sayles? He used to be at Woodrup, and Bob Jackson before that (started in '71), probably other postings too, but now he makes frames under his own name. He's very familiar with 753, and quite an artist, beautiful frames.
https://www.flickr.com/photos/kevin_sayles_bikes/