Don't run an open element air cleaner. Hot underhood air is bad for power and economy. You want a closed air filter housing with a duct off the snorkel routed to draw cool air from beside or below the radiator. I run stock air filter housings on all my vehicles.
In a van, I don't see how an open element will draw in any warmer air than was already being pulled in? The stock filter element was less than 10" diameter by 3.5" tall in an enclosed housing with a short snorkel. The snorkel had maybe a 2" diameter opening to draw air from as far back as behind the alternator and never had ducting from the snorkel forward to a cooler air point.
The 14" Diameter by 3" Tall Element should provide about 25 more square inches of filter media and with unobstructed airflow compared to stock, allowing the engine to breath more efficiently. The engine is essentially a large air pump. Given that the inlet air temp will be very likely the same, the easier it is to draw air in should result in better performance.
All that aside, i found a plastic spacer set and was able to space the 14" Edelbrock 1221 assembly up high enough to clear the AC Compressor. I put the plastic spacer between the stock steel spacer and the carb to maybe isolate some of the heat transfer. i know it doesn't make a difference, since these aren't high performance, but anything can help. Seat of the pants: It feels like the engine is accelerating easier. I already have a 2.25 dual exhaust with Flowmaster 40's dumping through the sides (through the rear of sidepipes), so the only exhaust limitation is the manifolds. I am also running an old Edelbrock 2PSP intake, so I am not reaching RPM's high enough to need any more flow.