> these are (old) hi-fi speakers, so the sound might not be best for guitar
Very worth a try.
IMHO, these are not modern "hi-fi" speakers. They are old-time radio speakers, assorted to cover a wider range. The Ten has good bass but gets erratic and beamy above 1KHz (especially in a pair). The Fives are sweet above 200Hz to 2KHz and a bit beamy to 5KHz; a dozen(!) offer pattern control (column, siren, semi-hemi?) but no 10KHz-20KHz top octave. The horn does that. The result covers ~~60Hz-15+KHz more or less well, and looks VERY impressive. Might be very lush. Could be plenty loud all across the audio band. Surely isn't as smooth or flat or coherent as many other hi-fi speakers.
Anyway, I see nothing to damp the high-end of the Ten. It surely sings well up the guitar band, though like any Ten it gets beamy on the overtones of the guitar top octave. The paper and corrugations are similar to many popular guitar speakers.
When a speaker is For-Guitar they may stiffen the suspension to support the bottom note and juice the apex for screaming highs. So it may not compete with a For-Guitar speaker. OTOH the bass can be brought up in a small sealed box (try 1 cubic foot) and maybe you don't need screaming highs. (Might be good on an "icepick amp".)
The pile of Fives is also interesting. 2 Fives with a few Watts of good tube power would be a fine parlor amp. 8 Fives in a mini full-stack (or 24 as a triple full-stack!) might be a fun "backyard stadium" system. My instinct says, for guitar, to trim off the wizzer cones; guitar does not want much over 5KHz. However try one with/with-out before you trim them all.
Home-priced tweeter horns from 1960 should be smashed and trashed. There were excellent high-horns back into the 1930s in movie sound, and a few more serious monitors, but not in domestic systems.