Great looking DP's.... and thanks for the pics.
Welding cast;
My best nickel stick rod story was the blade hubs on a Woods finishing mower. I hit a rock or something and busted one of the flanges off,pretty badly. Being a young homeowner with a bunch of crumbsnatchers,dropping the 70$ on a new one wasn't in the cards(big money 30 years ago). Went to the welding dealer and hardassed'm out of a cpl nickel rods. Did all the prep,welded fine,yadayada.
A cpl years later....
Kids are now dragging "stuff" around the yard and well,just being kids. I didn't see the short piece of C channel truck bumper? piece they had been playing with. Yup,hit it with the very same hub that had been welded. To my complete satisfaction,it broke in two places but NOT where I had welded.
Fast fwd. I Tig most cast iron these days with silicon bronze. Throwing it up on a yard sale electric griddle for a good long heat soak,at full throttle. Then weld it right on the griddle,cover with foil HVAC insulation "blanket".... ramping heat down over a cpl hours. Each weldment presents challenges on the "tacks". But have been thoroughly satisfied with the results. Not saying I won't go back to nickel,and stick... it works but,the Tig is so precise.
Good luck with your DP welding.