The big question is do I need to vent the washer bag so the bag works as a coolant recovery bag. Seems to me the answer is "yes" so it can fill easily and not have to compress the air that might already be in the bag, but I've had others say "no", not necessary.
That was a concern...but there's a '67 Fairlane 289 in for suspension work with that setup...that's what gave me the idea. Their bag is vented, but it came that way.
If it is a hard plastic like polyproethelyne instead of a vinyl bag, that would be fine. A vinyl bag will certainly be ruined if nice hot coolant flows into it.
i would just add a coolant tank,there are nice looking aluminum tanks that mount at the side of the radiator .i dont think the bag would hold up very long
I got a nice billet aluminum one off ebay for $57 delivered. Mounted it to the shroud, looks nice. Seller name was welder-joe. I know he had more of them cause right after I bought he posted them again.