2004R?
Is that in the same family as the 4L60E?
As for adapters for the Slant, I'm doing research on that front, and when I do find one, I'll be sure to make a separate post for our members to reference to.
The 2004R and the 700R4 are both non-electronic. The 4L60E is electronic. I always go with the non-electronic trans that way I don't have to worry about wiring and switches to control the torque converter. The 2004R trans fits in the 67 and up A body pretty easy, I made a very detailed thread on the mods and installation of the 2004R in my '69 Barracuda.