Figured I'd update you all on how this went:

I did a bad thing. I was in 4H on a paved road. I realized it, pulled over, put the transmission in park and dropped the transfer case back to 2W. POP! Whatever a "Park" is is now gone. Vehicle rolls freely in park. It's basicly another neutral. How hard is this going to be to fix?
Vehicle is a 1985 E-350 van w/460. C-6.

I turns out the problem was the spring that pushes the parking pawl into place had skipped of its stop. Super easy fix if you can find the right freeze plug. I took off the tail secion of the transmission, after draining, and peeked in to see the srping on the driver's side that activates the park engagement. It spun freely around it's shaft. In an effort to be fast not proper, i simply dropped the shaft out the freeze plugged hole, wound the spring around a turn and seated it, then stuck the shaft back in. Then I realized I needed to replace the freeze plug before I could seal the whole thing up and refill it. Local hardware store had a 1/2" plug that was too small. So I Ended up pluging it with a hand carved Teflon plug and some RTV. Works like a charm. 200 miles later, hits Park everytime.

Anyone who rebuilds these things know where I'd find the correct freeze plug and maybe a new spring? Not that I plan to monkey with it now, but in case I ever go back in there again.<!-- controls -->