As mentioned, every "105" 360/390 block that I have seen has the extra main webbing. The cracked block, assuming the outer water jacket is the only cracked area, is routinely repaired with the Lock N Stitch, pretty common stuff at machine shops. That said, if it was a 427 or 428 block, it may be worth the expense, but for a 390 block, personally I would look for another block. I understand that FEs are rather scarce in Europe, so that could be a factor. It may be a coincidence, but the few times that I have had a FE block that put oil into the cooling system via the passage inside the bolt, has been on a 105 block.
Yeah, I've seen this method. Am not really a fan. In case the laser welding turns out to be too expensive, I might consider it.
Looking for another block is really not that easy over here. We have a fraction of the amount of cars/trucks over here that you guys have. And what is here, usually was an enthusiasts vehicle from the day it touched European soil, means they're better taken care of, not lightly discarded. Virtually zero examples can be found in the few wrecking yards we have left over here.
I looked for a substitude block for 3 months and found only 3 offers:
1x 600 miles away in Berlin for 1600€ (1500$), alledgedly standard bore diameter, pictures showed that it was dragged over a concrete floor on all its sides and on the main bolts
1x same distance, only 600€, but already 4,10" bore diameter, I would have had to buy new pistons/rings
1x the one I bought. Cost me 1100€ and is cracked. Probably would have been cheaper if I had spotted the crack on the spot.
I'm willing to pay up to 500€ for the laser welding. If it is more, I'll probably take the bullet and keep looking for another block. Or consider the stitching method (which my machine shop guy also recommended)