I would NOT Advise to do something like this. The area you are filling is the area that the coolant goes into and COOLS the block. Once you fill up that area and only are left with those small holes as passageways to cool the block, its NOT really going to cool anything. Its just too small.
Especially in a daily driven situation, you need all that area for the coolant to pass through. The only way we do a "block fill" is on full race applications and even at that, of all the engines we're boosting 40psi with arent even FILLED like this way. At 45-50psi B-series block is when you consider doing something like this. but its not even totally necessary.

From our experience, a D-series stock UNsleeved block can hold 250-300hp in many cases. We recommend sleeving it if planning to go past that.
B-series can hold 400hp UNsleeved, but we recommend sleeving at 300HP+.
It looks like it might work, but you have to think about the actual NEED for it. If you are planning to boost alot anyways, I'd look into sleeving already. At some point, the stock cylinder walls are going to give out and not hold the power even if you have it FILLED.
Just my 2 cents. If it did work and was the good way of strengtening the block, everyone would have been doing it already.

In comparison, here's the real picture of a SLEEVED Open Deck Style block. the Closed Deck Style is not necessary unless in high boost applications, but the Open Deck is actually strong enough for 35psi boost.

 

what keeps those open deck cylinders from vibrating? just their own rigidity, or is there some kind of brace down a ways? and whats your official thoughts on block posting? i am not sure about it, but i think i like the idea better than a blockguard.

 

The open deck sleeve is installed by CNC cutting the original sleeves about half way down. The Iron Ductile Sleeves (open and closed decks) are press fitted into the block at about 10K+lbs of pressure. So it still uses the orginal sleeves to hold the thicker sleeves in place. All Sleeves are installed this way. Its not going to vibrate or anything like that. its pretty rigid on the block.

Block posting, I dont think is necessary. THe time and maching you put into the process is not worth it. Its not going to make the block hold 100-200hp more than it can hold. A stock cylinder can hold alot of power already. While its recommended to Sleeve at 350+HP,(b-series) I've seen stock cylinders hold up in the 450-500hp range. Block posting may strengten the block, but my point is, why do it if the block can already hold it at plenty of HP.

Same thing as a block guard. I would rather not use the block guard at all and just depend on the stock cylinder walls. Like i said, the stock walls can handle good amt of power, if the tune on the car is bad already, the Posting, the Sleeves, or block guard isnt going to do any good. It all comes down to tuning the car properly so its not going to give out. thats what you guys should be focusing on rather than posting or blockguards.

 

I just had this pic on my computer, sorry, I don't have a link.