There are all sorts of mustang II-based front ends out there, such as Heidt's or Fatman, and they have been working for years. I believe with most of those setups you keep your existing framerails. The aftermarket is full of upgrade parts for this basic setup. The same basic setup was used on the Granada so don't let someone tell you it isn't strong enough.

The Dakota swap is very popular here and it looks like that's because it is a good one. People either swap the whole frame or else cut and weld the new front end to the old back half of the frame.

I wonder when Dakotas are going to become scarce, they aren't really valued for much else and they are scarce on the roads right now. Probably quite a few sitting besides barns, though.

The Crown Vic is way too wide for a '50s car and there's no easy way to narrow it, as the crossmember is an aluminum casting. The rack and pinion is another problem. Hard to make it shorter...On the other hand, the Crown Vic would be just right for my '50 Buick, now there's a thought.

R.