Help with Ruff Stuff Diff Cover bolts for Chrysler 8.25

[glend]

Folks, I am trying to mount a Ruff Stuff Diff Cover on my Chrysler 8.25 rear diff. This is the cover:

http://www.ruffstuffspecialties.com/catalog/825COV.html

as you can see it is way thicker than stock and before I remove the thin stock cover I need to know if the stock cover bolts are going to be long enough to mount the 1/2" thick Ruff Stuff cover? I suspect they will not hold it.

The stock bolts are:

Hex Flange Head, .312-18x.562 , which sounds to me like it's a 5/16" bolt just over 1/2" long and thus probably too short for the thicker cover- is this correct?

So the second question is where the heck can I get longer bolts like these in Sydney? Would any flange head 5/16" bolt say 1" long do the job?

Any ideas appreciated.

[SteveC]

most bolts are rated by the marks on the head
Measure what you have and add the thickness difference
Then hunt down same rated and tpi bolts. Good chance youll find them at bunnings but take a sample with u

[Hunno]

Take one of the top bolts out & take it to an engineering shop with the new cover. There was a thread about where to get bolts from not that long ago.

[Steve F]

I use allen head bolts, so much easier as a normal bolt head can get very tight on the thicker covers. I think I got mine from Coventry Fastners

Cheers
Steve