340 or 318 turbo

I've decided to go away from the modified stock exhaust manifold I posted earlier.
I started to weld it but about half way round I ran into contamination problems that were so bad that the rod would not even stick to the cast, it just balled up and rolled off. I'd say being a side that is directly opposite the port exit has pretty much contaminated it right through.I was going to persist but I figured this manifold would probably give me problems later with cracking because it is so thin where I'm welding it.
To be honest I wasn't really happy with where the turbo was located in relation to the intake manifold, I'm going to use some tri Y headers I have here and modify them to do the job and locate the turbo a little further towards the front of the car.