As mentioned by Howie, the Edelbrock and TFS heads have blind upper exhaust bolt holes, with a non OE looking "bulb" on the backside. Considering that I have never had any factory FE head ever break off an exhaust bolt that is blind, but that is very common with the open upper holes, I really see no downside to having all the exhaust bolt holes blind, other than "it doesn`t look factory". That said, the vast majority of FE engines in use these days are more recreational, and not likely to rack up many thousands of miles of daily driving, in all weather conditions, so I really doubt having the open holes will really be an issue for most FE owners.
Since the TFS, Blue Thunder, and Edelbrock heads, are in long term back order, (not sure about the situation with Barrys Survival heads, but considering he has them cast at Edelbrock, likely similar), anybody looking to obtain some aluminum FE heads might be wise to get these while they are available.
