Rear Panel Speakers for 91 4Runner ?

I see where I can replace these with either a 5-1/4" or 6-1/2", based on information at Crutchfield but is one or both a direct drop in replacement for the factory speaker? Any modifications needed for a 6-1/2"?

I've found directions, online, on how to install a new head unit. Does anyone know where I could find directions on the install of the rear speakers?

Door panel speakers can be a PITA. I've done every installation for my audio system so far, and I'd say the front 6.5's were the hardest. They were too deep for the door, so I had to make a 1/2" spacer on a lathe (I wouldn't have been able to do this without the lathe). The clearance issues are the big problem.

I have 5 1/4" speakers in the back doors of my 97 lmt 4runner, so I doubt the previous gen's speakers would be bigger. You will have to do some modifications for 6 1/2"s maybe even cutting some sheet metal out. Its not worth it if you ask me.

The head unit install takes a while because of the wiring harness. It really isn't that bad though, just make sure all the wires are connected really well.