There are a lot of people offering Mustang II kits. Go to Google.com and search for "Mustang II Suspension Kit" You will get a ton of hits and can study the various options available. You might even find someone who has put one in a Merc.

One other thing to think about is to set your Merc body on an entire frame from a newer donor car. That way everything is updated front to back. Treekiller is doing that with a 53 Buick onto a later Olds frame I think. You can even keep part of the firewall from the donor car so you have the steering column, power brakes and A/C and Heater parts. If you need new floors for the Merc you can leave the floors from the donor as well. It's something to think about at least.

Pat