The 1980 1200 has an H165.

You can use a lancer mitsu diff, strong and narrower than others.
Get a locally made phamtom grip copy and although not a true LSD
it will be enough for what you need without breaking the bank.
Lancer diff are cheap and ask rallycar1200 for the PG copy.

Yes, just use the standard diff that's already in your 1980 1200.

so my standarded diff in my 1200 would i be able to put a h165 in it or h145 in it and where would i find one of these and what is the price range???
cheers

i run a a12 charged and only have a h145 welded and no probs yet but id go to at least h165

nicly said :)

haha not just antarctica, a locked diff will completely change the behavior of the car making it much more predictable sideways, exiting corners etc. .... that is unless you're not used to it and can't drive, then it could tend to snap out and understeer into corners etc.

Antarctica hehehe

Yes, you are right. Welding the spider gears if done properly won't break anything.

Now if the diff is marginal for the torque output of your engine, then a spooled or welded diff can push it over the edge. Just like slicks will. With the H145 & H150 you are more likely to break and axle when the diff is welded -- if you have a high-torque engine.

Certainly for Antarctica you need a locked differential.

weld'd diff's brake ? i beg to differ