I could be way off on this, but if I'm not mistaken don't replacement rod tips come in different sizes?

If so, does anyone know what size I need to replace the tip on a Berkley lightning shock?

I'd call the manufacturer unless you have a tip gauge laying around. They'll probably give the size in 64ths of an inch.

Thanks. I'll see if I can find some info on the net before I call. Probably shoulda just done that in the first place.

Take it to a tackle shop and match it up.  They will usually replace it, labor and all, for cheaper that those kits.  Be sure to get one that will hold up to braid.

I've used the Walmart kit a few times. The eye just needs to be close to the same size. I don't have a tackle repair shop close

You can use the Walmart kits as mentioned. They come with a buch of sizes and one will fit your rod I am sure. I used one before in a pinch but later removed it and put on a real tip. They kit had terrible eyes and they were huge but they will work. For your rod I am sure it's fine and wouldn't worry much but on a higher end rod it was only temporary.