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.
Two totally different transmissions. From the factory, GM typically used the TH2004R behind low horsepower /low torque v6/v8 engines while the 700r4(as known as the 4L60) was used in Corvettes, Camaro's, cop cars, and light duty trucks. Both can be built to withstand more HP than GM intended, but at a cost. Behind big blocks GM used the TH400(3 speed) until the 4L80E(4 speed) came out in the 90"s.