Ahhh Big Block Rock!!!! Log on to HotRod.Com, and check out an article late last year on filling up to 400 cube small block Chev's. A V8 is easier to fill up with grout, as it has natural sand casting ports. You can fill 1/4, or half or even 3/4's up the water jakets depending on the application. On the Ford Six, the front water pump hole has to be fairly clear, and you just calculate the amount by filling the block with water to check. You've got to fill the camshaft side, and then get the air out. Best to tip it to the cam side with half fill of grout to the top of the frost plugs, tap with a brass hammer, and then leave it level with the grout comming out the bottom of the frost plugs. The thin-wall castings are unable to be supported at the top like V8's.
Lastly, number one gets way too much cold water. If you can figure a way to encase it, while still allowing the water pump to bolt on and flow h20 to thae back, then you'll add a huge aount of strength, and possibly safegaurd an 80 thou overbore.
Get some other advice, but that's how I see things.
Beats going for a long walk in your concrete walking boots at high tide after the engine splits a wall