I never saw the big deal of DIN tanks but that's another thread. The later AK or later Phoenix are your only options for a DIN DH or as tbone said, use a valve adapter. You also have a second problem, DH regs (except the AK or Phoenix mod) do not have any way of monitoring your tank pressure. You have 3 options, use a banjo, use a J valve or use a tank valve with a HP port. Of the 3, I prefer the J valve. They are easier to find, work on all regs and you don't have to move the SPG or have multiple valve/SPG combos. Old steel 72s with J valves are common so a dedicated tank for your DH is not a bad way to go.
I will correct tbone a little, all common USD/Voit DH regs are easily serviced, the difficulty goes up fast from there with some very common regs (Dacor esp) being almost impossible to find good service parts for. For your first DH, either go with an AK if you must have LP and HP ports, if one LP port and a J valve will work, then find a DA Aquamaster (DAAM) or Royal Aquamaster (RAM). The Voit equivalents are good as well but often times come at a higher price as they are harder to find (if you stumble on one at a great price, buy it, sell it and use the profit to rebuild it's USD cousin) The USD Mistral is a single stage reg so if you can deal with no LP at all and a J valve, it's also a good reg for your first DH. If a single stage reg will work for you, one other option is the Healthways Gold Label. You can find service parts for it and USD hose loops work perfect on it. It's the only non USD/Voit reg I would recommend for a first reg.
You also need to consider how you plan to hold your tank. Modern BC's do not work well with DH regs. Unlike single hose regs, a DH reg (vintage or modern) is sensitive to reg placement. They will work and supply you air but their performance is hurt a lot if you ignore proper placement. I prefer an old Kam-EZ or similar BP, a simple harness works as well. The more common blown plastic BPs (about an inch thick) are not acceptable, they are too think and don't allow the reg to be placed low enough. If you need/must have bouyancy compensator, then your best bet is a VDH backplate with small bladder. Do not underestimate the need for proper placement. My AK has better performance than a top of the line Scubapro or Atomic but you can only experience it with proper reg placement.