Q: What version of Safari will work with OS X 10.5.8

1. Safari 5.0.6 is the last version compatible with 10.5.8.

2. Use the Software Update pane of System Preferences.

(111530)

I might recommend you consider using TenFourFox. It's a brilliant browser that propels older Mac OS versions to enjoy a modern browsing experience.

http://www.floodgap.com/software/tenfourfox/ Check it out.

Safari 5.0.6 for Mac OS X 10.5.8 

Another option that has more current update than obsolete Safari,

is a shareware that will run free (with occasional prompt to buy)

from iCab via download from web site... http://www.icab.de/dl.php

version: iCab 5.1.1 (13.09.2013)

(Universal Binary)

for: Mac OS X 10.5.x - 10.7.x

(G3, G4, G5, Intel)

direct download: zip (for 32/64 bit)

http://www.icab.de/download.php?os=UB64&lang=en

I've used this along with other browsers in Leopard 10.5.8 and

find it adequate; yet have not paid the license fee. It works.

And does not require registration.

Good luck & happy computing!