One good thing GM did was continually improve the 700R4/4L60. Most of the late model components will fit on the early ones. I know the early ones had problems with the pump and forward sprag assembly. I've also seen the planetary come apart on more than one.
It's been awhile since I've had one apart, but I will recommend getting a shift kit like TransGo or another comparable. They have springs, valves, etc... that solve alot of issues.
