Actually, the 2004R can be beefed up quite nicely. Got a bad rap early on, but I have had very good results with them. Could handle whatever the 317 could throw its way if built right. But the bolt pattern may very well kill that idea any way.
I don't know what year the bell housing pattern changed, but I had a 1960 Pontiac with a 389 that had the standard BOP bell pattern. It had a 4 speed automatic in it, but it has been so long I don't remember what it was.
But I see lots of folks sell the 2004R short, when it can be a very stout transmission.
