so it has been a while, but here are the things I ran into.
I put one in a 65 coronet, but it had a poly 318 not a slant 6.
schumaker makes conversion mounts for /6 to v8. but not sure how it handles 318 vs 360 mounts vs bb mounts you would have to check.

727 vs 904. I used the original 318 converter, so it was neutrally balalnced. b&m used to make a flex plate for the direct bolt in of a 5.9 to a 727 and it was balanced for it. The holes don't line up for a 904 and they didn't make one. BUT I read some people slotted a hole and it worked. never read further on it.

power steering- 2 things here. get a van bracket/pump. otherwise the truck one will put the cap under the battery tray. the van tucks it in closer to the engine.
for the hose, I found a hose shop near me. lots of them over town and had them customize the ends and length so I could bolt it up to the old power steering box to the new pump. Some have mentioned it might be too much pressure, but I haven't had any issues so far. been 10 years I guess now.

I used the original alt that came with the 5.9.
not sure on your car but mine has the single field voltage reg. I grounded one field wire and ran the other to the single field vr just like any other dual field vr and it works fine.

The alt bracket also includes the a/c mount and the idler wheel I think.
a/c mount is different between vans and trucks.
I found I needed to modify all that swaping between the van pump vs the truck pump to find a belt to give me better wrap.
I got one thet worked originally, but decided to find a better one.
by swapping the idler with a 5.7 hemi one, I was able to find a factory 5.9 belt that worked, that was for a different model.
not saying you can't get a van one to work, but it wasn't ideal routing to me.