Modifying vent boxes

[Spook50]

Once I get my Duster back on the road (needs a new radiator) I want to first pull the vent boxes, clean them up good, then have them powdercoated and install new seals in them. I'm also thinking about putting some sort of wire mesh inside to hold a piece of lightweight foam to use as a filter of sorts. I'm not concerned with going all-out and using a Hepa filter or anything like that, but I'd like something that'll catch dirt and crap that would come in through the vents. Anyone done something like this? I'm thinking the foam that you put around the filter on certain Shop-Vacs would be a good way to go for this.

[bOb shingler]

the hair a/c filters might work out good also.