JBL L-300 Summit Are they still any good?

Why do you want to change the L-pads, are they bad? Just remove the assembly from the cabinets and clean/lubricate them well. I doubt you'll find L-pads nowadays like the quality of the originals. If you're not going to bi-amp with an active crossover, I would replace the capacitors.

Clean them up and turn them up! 

I definitely will once I get the other L pads cleaned up.
great care is being taken not to damage the consecutive serial number foil cals. With all the L 100s I’ve restored I definitely have it down to a science.

Actually, there is a lot you can do with the L300. They can be restored to sound like they did when new. The diaphragms in the midrange and tweeter can be replaced if necessary, although the tweeter diaphragms are no longer manufactured by JBL. Radian manufactures an excellent replacement for the mids. The tweeter phram may take some time to source, as most folks don't recommend the Chicom replacements. Nelson Pass designed a replacement crossover that eliminates the inductor/autoformers. Search for his article on the internet.  

Thanks for the information. Do you know how I can find the new replacement diaphragms ?

Great, I love the older JBL's. I have a couple pair myself. Glad you know what you are doing. For me, Clarity or Mundorf caps, a source  Capacitors: Madisound Speaker Components (madisoundspeakerstore.com). Not sure how their prices compare. New diaphragms can be found on ebay if you are persistent. I would NOT change diaphragms unless they are really needed. Originals are the best unless they are auditorily defective. Watch out for made in China copies, they are not good.

If the 077 prism tweeters have the blue ring diaphragms, they sound better than the newer gold ring diaphragms and you simply cannot find the blue ring diaphragms as replacements. I've been watching for 10+ years and only saw one on ebay and missed it. I have one in case of a failure!

Thanks for your information pulled the other speaker apart today. Just fired them up! For old cap’s they still sound good. I have done a lot of business with Madisound with all my L-100 restorations. I still have a ton of the LE 5-2, mid
LE 25-1 tweets and 8 123A-1 and -3 woofers. I need to start unloading the extra parts. I watched a interview with Nelson Pass he said he may have improved the L 300 crossovers a bit but still felt  JBL did an excellent job on the configuration.

Yes JBL was one of the top back then, older ones, 60/70. I'm sure the caps are still good enough. As you know, they have made some improvements in capacitors since these were made. Could have already been upgraded I suppose.

@iconicaudio,
You might want to check out the Lansing HERITAGE site you will get more info on all things, JBL and ALTEC. Yes, they are good. Mike

http://www.audioheritage.org/vbulletin/showthread.php?28611-JBL-4435-by-Guido=

Lansing Heritage has a wealth of knowledge. I am just so busy listening I haven’t had time to even go on the site. I bought these at an estate sale from the original owner. I am not quite sure how common consecutive serial numbers are with the L 300 but these are consecutive serial numbered.All the drivers and components inside are very close in serial number.
The cabinets are in pristine condition not a mark on them. 

I clean my JBL very often. may be you have to do that toohttps://ludokingmodapk.xyz/