'88 300SEL - clunking when shifting out of drive

[86560SEL]

Hi all. I am wanting to get my '88 back on the road, but it hasn't been driven much over the last couple of years (other than moving around the driveway every couple of weeks) and while it will roll, the brakes are very tight all the way around. Working on that, but I have noticed when it is in drive and I shift into park, there is a clunk. Any ideas? Flex disc?

Thanks.