The only real advantage is the thick main caps. Same as the 289 hipo caps. They are basically same as the early block as far as main strength goes. In the us they appear to be worth 200 - 300 dollars. Mostly found now from the trucks they were used in. In my mind not worth the trouble over a pre 74 block.
Sorry to say I understand the Higher Nickle content is a urban myth. It is not true.
Luckily today, if you want a super strong block get a new Dart block (or equivalent as there are alternatives to Dart out there). Otherwise in the 302 family range the early 289 hipo, then any other early pre 74 block, then pre roller block and lastly the thinner castings of the post 84 roller blocks.
Today, we can build a totally new small block ford engine in every respect without using a single ford component.
I think they make the new Boss Windsor blocks in Mexico, I think they are made on the truck diesel line with the truck engine iron which is certainly better.
Understand. If your under such a restriction to use used factory parts for block and heads then (assuming capacity is allowed) then a early 351 Windsor block with Cleveland heads is the best combination.