For my build, I was recommended something in the 260's @ .050 and around 0.650" lift, so similar to yours. I've got a Victor 383 intake and a few 4150 carbs to choose from (2 different 950's and an old school Holley 4781 850).
Access holes are the only way to go in my opinion. That's the route I went on my '66 Dart. I also went with socket cap bolts on those top two to make it easier to feed the bolts through. Makes taking the transmission out a whole lot easier, especially in an early A body.
Let's not forget that as the cost of production goes up (labor, regulatory compliance, etc), the profit margins get thinner and thinner. Costs end up getting cut somewhere. It gets really easy to see why a lot of this **** gets outsourced oversees.
I don't think it's the copycat **** that's getting them in trouble. It's the fact that they actually put the dude's business name on it. Dude's lawyer should have a field day with this one.
I just used paintable urethane seam sealer, but I wasn't too concerned because I made a flange around the complete perimeter of the bulkhead to attach it to. In your case, I know they make a fire-rated caulking/sealer for the building industry. Maybe something like that would work. Do you plan...