Hi,
When you had the dash out, did you have the negative battery cable disconnected? If the battery was still connected and you moved the dash around that may have caused your problem. Always disconnect the battery before doing anything in the electrical system, even if you think you don't really need to.
Most auto parts store replacement fusible links will usually just be the plain link wire. It comes in different gauges and most stock links on these cars were #16 gauge. You will most likely need to replace the Packard pin connector on the new piece of link wire. They are called Packard 56 type terminals and the parts place may have them. Another option is to replace the link with a more modern blade type fuse called a Maxi-Fuse as used in newer cars. That way if something like this ever happens again, the fuse is easily replaced. Replacing fusible links is a bit of a project. With a stock alternator a 50 amp Maxi-Fuse is about the right value. I use a NAPA NW 784482 Maxi-Fuse holder and a RED 50 Amp fuse.