Wow... nearly an identical system to my A4k. :-)
I have successfully re-kicked my A4k to 1.3 using various tools, but I wouldn't recommend it. Very unstable -- and not much benefit.
AmigaDOS 1.3 was a different beast. There was no 040+ support to speak of. Fast RAM was considered to be a Zorro2 kind of thing -- and 8 megs was a lot... Lots of more modern features really trip up the 1.3 ROM.
Plus, most stuff that needs 1.3 will also not like things like a CyberStorm '060, 64MB RAM, etc.... And, since there is no fallback processor on an A4k, you're pretty much out of luck. (Trying to stack together a command to go to "kick 1.3, no cache, privledged mode, noAGA, 50hz, 512k chip, 512k ranger" isn't easy, and rarely works.)
I keep an A500 and an A1200 around for playing games when the urge arises. :-)