I get it, but the humor I see is the OP bought it. I would not of taken it home from free, unless I had a boat, as you say.No sense of humour???
If it was mine, I might fix it myself just to see how long it would hold up. I've had great luck welding cast iron with a Tig and SS filler rod.
Stop-drill all the cracks, and v-groove and weld. 99% of that manifold isn't structural (I wouldn't lift a motor with it), and the most pressure it sees is 16psi or whatever your radiator cap relief is set at. Thermal contraction and expansion are your biggest enemies but since it isn't structural and it's a huge heat sink, it might be fine. Worst case, you get an intake leak or a coolant leak. Intake gaskets fail on the regular and nobody dies from it.
Try it and see. I just wouldn't pay some other slob to fix it.
Internal or external leak and is it worth taking the chance to hydraulic an engine. Here I’ll answer for you. NO IT iSN’T.
To me it looks like it was in a puddle outside and froze. Yes it could be cast iron welded, but to weld all those cracks is going to take a lot of time. The problem is the weld area has to be preheated and then cooled slowly to prevent cracking at the edge of the weld. All of the crack has to be ground out or the crack can start to propegate again. In my opinion the cost to repair will be as much as buying a good core 340 engine.I have very little in it, $150 to fix would be worth it to me