mines matched up to the outlet of a 75mm tb. if you looks at just the inside of all the plenums out today they are really all the same thing. depending on how much material you take out you can probably land anywhere between stock and tops with a p&p plenum. for me the 1-2hp/tq gain with some 150-200 piece that i didn't even like the look of seemed like a waste.
as far as bigger, most of the new plenums have basically a spacer built into it on the bottom. i used a spacer and then ported it to match perfectly.
the debate will go on forever with these things. for the 40-240 range a plenum costs i'd say get whatever you like the most.