[bobbader]

In my opinion, you're working in reverse, thinking that this may be the only problem with this engine and a patch will have you going merrily down the road. While many would dismiss this block right away as not worth the effort, only you can determine the effort you want to expend and $$$$$ you want to spend and whether this is necessary given it's a non matching number unit, hasn't been run in years, etc. If you're dead set on making the gamble, the wisest choice is to disassemble everything, degrease the engine, take it to a reputable shop, see if it can be magnafluxed as is, or will need further degreasing and rust removal before doing so. My guess is that, even before you get to the magnafluxing, you'll find enough other reasons to abort using this block. If your intention was to have an engine rebuilt, find a rebuilder who is well known and trusted on this site or through club members or other owners and start fresh. Many rebuilders will have a stock of rebuildable core blocks or complete engines at "going rate" prices that make searching among piles of other unknown used engines a useless process. After 40+ years in this business I can only tell you that if one mechanical item on an unrestored car has an issue like this rust hole in your block, you're search will most likely turn up other concerns. If after disassembly, cleaning, bead blasting, and magnafluxing, someone deems this engine OK to use or rebuild, go for the best possible scenario of repair that others have suggested.

Good luck,

Bob Bader