I have a 120 000 btu mid effcient furnance, mid 90s. Also a central air
tied into this as well.

The original return air filter box is an old electro-air electronic filter
that no longer works. The electric contacts are burnt out on the housing
and the cartigages. I'm debating about having to replace this with a new
electric filter or a paper type filter using those 4" wide filters. Right
now I cannot adapt any current paper filters into this old housing because
it's 3/8" shorter than modern housings and the filter get crushed or distorted
when inserted.

The one main criteria is I have two big dogs in the house.

Anyone got any advice? Thankee.