WEll............

The Mex blocks are about 20 lbs lighter than the tonawandas, they shaved metal off for weight savings. On the bellhousing bosses like I mentioned, but also in the crankcase webs, and very importantly also in the cylinder bore thickness.
So as a consequence the Mex blocks are not as rigid or strong as the Tonawandas. Also you can only rebore them .030 Max in the majority of cases.
Also another factor is the metalurgy, there is no tin or nickel, they just use cast iron as a consequence they wear fast and can be porous.

In my opinion you are better off with a Tonawanda 2 bolter. they take up to 500 Hp as a conservative figure with 2 bolt mains. If you want 4 bolts get an eagle 4 bolt main conversion kit for $69.00 on Ebay, they are the angled caps, but if you do this also know that the block must be align bored. Then you have strong horsepower foundation for your next project motor