I am pplanning to use a de -dion but.... I was going to use x1/9 frot hub as I have Fiat wheels (long story), and spent £100s on recon parts. If I choose to go the De Dion route I don't think I can use those hubs but could I make a hub??? Buy the bearing and thick wall roun tube and preston weld the de dion to that. the caliper could easily be adapted. Or can I cut and weld my existing hub (welding onto cast iron??)?

The hubs should be cast steel Alain.

yes, you can make hubs if you have a lathe then not too tricky, but as Pete says, the ones you have should be cast or forged steel, so weldable anyway.

Does this mean I could cut my existing ones and wels brackets to them???

If you are going to fabricate uprights or modify others, just make sure your welding is up to snuff as its a relatively high stressed component. Cheers!

yes, you should be able to cut and modify your uprights, though making ones from scratch may end up being easier, and of course cbrlfrost's comment is dead right, they need to be done right, obviously it's not a bit you want to break!