1964 Crown floor pan

[Mark and Theresa Elliott <deadfishe@xxxxxxxxxxxxx>]

I have recently removed the carpet from my Imperial, and I am now in the 
process of scraping the remnants off the floor pan so that I can address 
the rust.  What is that stuff?  It looks like undercoating.  Was this 
normal?  Was there paint under it--I can't tell, about all I can see under 
it is rust or what could be either bare metal or 
primer/paint.  Surprisingly, even with as much rust as there is, yet again 
no rust through.

Also, the bolts that hold the body to the frame (at least I presume that is 
what they are for) seem to be quite rusty.  Are these special bolts, and if 
so is there anywhere that I can get them?  I figure as long as I have 
things to this state I may as well replace them (plus I would hate to have 
them break when I really need them).  Is there anything else that I should 
replace while I am replacing the bolts?

Thanks,

Mark Elliott
1964 Crown 4 dr