I love my cowl vent but sealing it from water can be frustrating. If you have A/C I could see how it would be unnecessary, but if you don't they can be a life saver on those hot summer road trips.
Sidenote: I can tell you that water under the dash or coming in through the cowl vent in a downpour when you forgot to close it isn't as big a deal as you'd expect.
Instead of using one of the chintzy plastic under dash thingys that come with the Vintage Air heater to mount the control knobs, I welded up some metal to make a more classy unit, to be painted dash color.
Been working on fabricating the fan shroud, installed today. the 17" flex fan just clears the lower rad outlet, needed to make a cutout at the bottom of the shroud to allow fitting the rad hose - seems like everything always wants to occupy the same space at once