Summit sells the 4.00" Eagle 4340 steel crank for $700, I'd use that way before I used a welded crank
Just wondering why if you want a 4" stroke crank, you wouldn't consider a 454 crank which is 4" ? Not sure if they are steel or not or how important that might be per your build. You can pick one up through Summit or Jeggs relatively cheap. I used one in my 348 which I'm told did require some internal machine work. Works fine thus far.
To get a 454 crank to fit-1)turn down mains,2) turn down snout to SBC diameter 3) turn down counter weights to fit in block, 4) balance-might take heavy metal to go internal balance.
I knew there were some other fine tuning. You end up with more machining costs than a new one. Why I still have a 454 crank sitting around.