Anyone know if 3.5L SOHC heads can be welded sucessfully or safely? Or even if it's recommended?

Talking welding inside the combustion chamber for re-shaping work.

as Buffy said its possible, but it aint something I'd be doing in a big hurry.

Get it wrong and the results could be disasterous, not to mention that you really need a flow bench at the minimum to get the reshaping right.

I talked to a couple of head guys and they strongly advised (several actually refused to do this, a couple said they would do it but gave a 30 second/3 metre warrantee) against it - you need to remove the valve seats as the heat warps the chamber and they get out of alignment in regards to the valve stems (so you need to take them out anyway and regrind).

The head would need a skim, and not sure how much warpage would occur from the heat, but Mitsu state no more than 0.2mm to be removed. You also need to use a TIG with a very competent welder - the other issue is that the alloys (between the weld and casting) are different - so while they will stick, you have all sorts of interesting issues at the interface - different expansion rates, thermal transfer rates etc + grinding could be interesting, if one is harder than the other - possible, as the alloy is pretty soft.

Cheers
Heath Young