We have welded several pickups for monster trucks ,usually tig, and stainless.

but if the piece is cast iron the best rod to use on /A/C CURRENT Tig welding procedure is>> a-2 welding rod. which is aluminum/nickle bronze and we have welded several of the Mercruiser exhaust manifolds or anything made of cast iron.

I've welded CI by DC (I think) stick. Can't remember what rod I used (too many years ago), but I do remember that it was a special rod.
I know you should preheat the material to several hundred degrees prior to welding to prevent thermal shock. Then stopping every so often to reheat the material and allow a slow cool down at completion.
CI gets very brittle during the welding process. If not done correctly it will fracture along side of the welded area.

Sounds like you've got a good welder working for you.
Good job.

I believe preheat and weld with nickle Rod.

CougarMan I think you're right.
The use of a nickle rod sounds familiar.

Thanks for jogging the memory.

nickle/aluminum a-2 welding rod