I think I'd just wait and do it right with the entire 7M. You'll run into issues with the crank pulley and you'll probably have to fit the 7M pistons into the 5M block. That and its such a PITA to remove the engine again and do it all over. You might consider just getting a JDM engine and selling of all the extra parts, you might get lucky and break even. Hmmm I don't believe I've ever even heard of a bad 7M block. That engine must've had a hard life.