I would "think twice" about eliminating the vents. They are 'nice' on a hot day. Do you have the driver side airbox, so that you know what it is?
Options as I see 'em
1....Make a disk to cover the holes from the bottom, use a small piece of angle to make a "T" bolt, work the angle up in, put a nut below
2...Use stock air box on left, plug the pass side
3...Try to find ultra rare "heater delete" air box
4...Modify drivers side airbox to fit pass side
5...Modify early Mustang air box to fit. They have a cable controlled butterfly
See this thread
heater delete general questions
Rare "heater delete" pass side box
View attachment 1715698817
Mustang air box. I cut one down so only the butterfly is left (look where the pivot is) and mounted on the driver side of mine. This was done for extra clearance as that is where the fuse/ relay panel is mounted, as well as Holley EFI module
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View attachment 1715698819
