Yeah, the founders sold it many years back.

I guess the new owner ran it into the ground.

https://mack-products.com/ is the truck bed company. If I remember correctly Mar-K sold to them years ago.

The original owner of Mar-K sold the business in 2016.  A local OKC group continued operations.  They ran the business until recently and continued operation in OKC.  It appears the firm has declared bankruptcy and shuttered operations.  Our local truck club got a tour of the operation soon after Mark, the original owner, sold the company in early 2019.  It was an awesome experience!  I am uncertain there has been a connection with any other similar manufacturer during those periods of operation. 

@chip Mack Products is a company in Moberly Missouri that was the original reproducer of sheet metal for Model A Ford Pickups. They branched out into other makes and as far as I know they are still in business. I was not aware of a connection to Mar-K, not that I would know if it were the case. Moberly, Missouri is about 40 miles from me. Jim Carter told me today that he thought Mar-K was supplying all of the ribbed bed wear strips to the hobby.

Mike

Many years ago I had contacted both Mark Products and Mar-K about their reproduction truck and pickup bed parts. I don't remember the details but was told that the two companies were cooperating and coordinating not competing. There was not enough business for them to both make a part. 

I was told the problem for Mark Products is the old truck part business is not profitable enough to stand alone. They have to take people off other jobs to make parts and it is a desire of the management to keep making some parts as they are truck enthusiasts. I bought the remaining products for the early Chevrolet pickup beds. Some of the fixtures had been lost, damaged or not usable so it was likely they would not make any more of them.