Cheapest way to lock up a non sure grip?

Hello! I've got my hands on a 742 diff with a 4.86 open ratio. This one will only ever be used on the track. I currently have a 741 3.55 sure grip unit that I put together myself. Now I live in Sweden and it cost quite a lot to buy the sure grip and the other parts to renovate and put that one together.

I have to stay on the cheap side with this new one though since money is an issue at the moment. Is it possible to weld it, should I go spool, what are the options? It currently have the large yoke, I'd like to change to the small one, any tips on where to get it?

Thanks in advance!