I'm rebuilding some La Scala's and some Klipsch Horns......I would like some input on the best "stock Tweeters" for these great speakers.........Thanks
maybe ask it here: https://community.klipsch.com

Yes, shoot over to the Klipsch Forum.

Maybe check the Bob Crites website also.
I can't figure out how to get in the Klipsch forum......They seem to want everything but my pass-port.....autospec
"   I can't figure out how to get in the Klipsch forum......"

I am already a member there and I just created a " new " account and it took me not even 2 minutes to complete.

what kind of problem are you having ????
Addyson......I'm not a computer person so I have to take what I can get...And figuring out how to get in the Klipsch forum is not real high on my "to do list"  I really don't want to write a book on this, I just want a couple peoples opinions......

you dont have to be a computer person......I gave you the link and all you have to do is register. its not hard to do.

if its so hard....I will post the question for you over there....its no big deal and if somebody replies, can give you the link.

The original tweeter in all of these are the Klipsh K77, a Klipsch branded EV T-35. They are excellent tweeters. Originally, the diaphragms came with very fine wires attached, kind of like a human hair. They frequency burned out. But replacement diaphragms are available with beryllium/copper leads that will not burn out. 

Replacing the diaphragm will be tricky for the novice, but is doable. Or one of the speaker repair houses can do it. 

A big step up from the EV T-35 is the EV T-350. They are spendy on the used market and may require a bigger hole to be cut in the cabinet.

Bob Crites makes a replacement tweeter that  a drop in and is based on a currently available horn tweeter. They are not to my taste but YMMV.
The OEM tweeters are expensive, and more expensive in recent years.  I think it is the K77 as mentioned above.  I went to Klipsch themselves for them and they tried to discourage me from buying them.  Not sure if the same tweeter was used thru out the entire production run.
I have the less expensive Crites replacement in the pair of 1974 Cornwalls
not sure about SQ but Bob seems to know a bit...
i use them as garage rockers so critical listening is done with beer and power tools....
Mechans, as per my last post, the Electro Voice T35 is exactly the same tweeter. EV are the ones that supplied Klipsh these tweeters through the whole production run. No difference at all, and not particularly expensive either.
I have an old EV S12-S cabinet that may have a bad tweeter. It's the ST350A which has the round magnet like the older Klipsch K77. I replaced it once before.  I emailed Bob Crites about it and he told me there are NO good replacement diaphragms for these at all. He said the one's on eBay are not very good.

The Horn measures 5" X 6" and I don't really want to cut into the cabinet to fit a replacement horn/driver. I want to use the cab for electric and acoustic guitar so it may not be as critical but I'd prefer to rebuild the original if I can with something that will last.

Has anyone heard a good replacement diaphragm?
Simply Speakers has a replacement diaphragm 89486A but other than the reviews on their site I have seen much info on it so I don't know if it's just another supposedly inferior China import part.

I believe that virtually all of the diaphragms out there for sale are the Asian sourced parts. I have installed quite a few in T-35s and I am very happy with the results.

in one way, reliability, they are far superior to the originals. The original leads were super thin, like a human hair. The replacements have thick leads that don't burn out when conducting power. When you pull the old ones, it is inevitably the lead which is toast, not the diaphragm.

Installing them is not that easy, but if you have DIY soldering experience it is quite doable. Let's be honest, the EV tweeters are peaky no matter what diaphragm is in them, which gives them their characteristic sound which I, for one, like. I know, I'm deaf.
Viridian, thanks for your input on this, its always good to hear from a hands on person.....So many of the observations are made by people that do not have first hand experience with this type thing.....Thanks