I've also used a 1.21 venturi carb on a 2.8. When I ordered it I specified a 79 Mustang with a 302 and that's what they sent me. It works pretty good but is probably a bit more carb than is needed and it sometimes bogs down a bit (I believe because the carb is too large) when you hit the throttle hard. It never fully stalls so it's livable.
I again find myself doing a duraspark conversion and this time I specified an older eight cylinder application (75 302 Mustang) and they again sent out a 1.21 venturi carb (this was my mistake though, I meant to order a 2.8 carb). I haven't wrapped this one up yet but it seems like it's going to be the same story with the carb being a bit too much for the engine, but it still runs well. From my two experiences, I think you need to specify a 2.8 carb if you want to get a 1.08 venturi. My two trials both ended up with 1.21 carbs.
As far as going Holley or 2150, I thought the same thing and after much reading I chose the 2150, which is regarded as one of the best carbs ever made, by several sources. It works well off road. I have an 85 BII with a 302 and Edelbrock Performer carb on it and the 84 with the 2.8/2150 combo. We took both of them wheeling and the Edebrock equipped vehicle was constantly stalling at nearly any angle we put it at while the 2150 just kept chugging away, and this is even after a friend of mine who is very experienced with Edelbrock carbs helped me tune it (it also has the "off-road" kit installed), he runs them exlusively on his derby cars and he runs derbies all summer long, sometimes multiple a weekend.