First off, looks like all the bows I've ever come across (two trucks with old bows - but who knows if they are wartime.... - and two sets of new ones from different sources) may have the wrong thread in the bushes.
24 TPI would be 5/16 UNF. The ones I've suggested, and used, are indeed 18 TPI (UNC).
They are indeed socket head (domed). Hence my note underneath -"At the time I couldn't find any of the flatter head ones like Deadline has shown(more like the originals), you may be luckier". I thought they were a pretty good compromise, plus the stainless steel won't rust-stain the canvas (I couldn't be bothered to paint them :blush: ).
Vulture - sorry but I don't feel I'm qualified to offer any further help on this matter as I do have a reputation for being a bit of a bodger - looks like I've been rumbled. :-D
Happy Days :-)