First, I apologise for it taking so long to get photos. The bass is being stored at the deceased father's house and it's 20 miles away.
While there yesterday I took a bunch of photos, covering every inch of the bass in detail. I dusted it off but used no cleaning agent. There's a lot of cracking in the (paint), but there's no cracked wood anywhere I can see. I looked it over very carefully. We also found (2) $1 1935 E dollar bills inside of the bass body. I managed to fish them out, and they're probably keepsakes.
The soundpost is in there. It appears to be in the correct position. On the second photo I drew a red dot where it approximately is. Based on the scuff marks on the dust inside of the bass, and the tight/perfect fit of the soundpost in that position, I have reason to believe this was where it was orignally set.
I'm not sure what the metal piece near the "epiphone" logo is. There's a patch cable with the bass but the end doesn't fit that metal piece. I was thinking it was some type of pickup, and has a threaded end.
So I'm feeling confident that the bass is ready for strings. I'll keep the old E string on, add the D, rmoved and replace the E, add the G, and last the A (unless someone has a better plan to keep the tension on a one-string bass

). If I hear anything cracking or notice any exagerrated warping of the wood around the sound hole I will immediately stop and bring it to a local repair shop.
Thanks again for all the advice and my knowledge of double bass guitars has grown exponentially just being involved in the process.