I finally found a 250 that I've been looking for. The best thing about it was that it was near home! I got a '76 250 with 60,000 on it from it's original owner (his Mav LDO 4 door was t-boned some years ago and he kept the power train) along with the C-4 for $150, as well as with a few other items in the deal. The seals appear to have held throughout storage and the crank turns so hopefully by next year, it'll be ready to install. Now I need an engine stand!!!
Congrats on your find! Sounds like one less thing to deal with, pretty cool that you found it near you!