904 sittin for a decade?

Alum/billet drum, pro transbrake, etc, it might be worth that.

$2500 for a rebuilt 904 and a $200-250 converter.. Not to me.

It's maybe 600 on a good day and would have to be guaranteed to work at that price.

If you are mechanically inclined, they are EASY to rebuild. You'd have $200 max in parts. I have a 727 dvd which is very similar to the 904 or get a ATSG manual for about $30 and do it yourself. They aren't rocket science.