Google shows a couple of hits for DC-3 type ratings at about $14,000 . . .
There's an AOPA article dating from 1994 saying the airplane costs $625 an hour to fly, figure at least twice that at today's fuel prices, maybe 3X.
EAA has a type rating program for some of these older airplanes as well - no prices shown, I think you need to bring your own B-17.
I think I'd first try to find someone who is operating one of the aircraft of interest, then ask them how to get a type rating in it. Example - Red Bull owns Franco's (I think) DC-6 and flies it to air shows - contact them, the airplane is magnificently restored.
You sure have picked an expensive hobby - wonder what a B-52 type rating costs if you're not having Uncle Sam pay for it ? (big grin)
Best Regards,
Echo Mike