Food for thought for your swap.
The 700R4 and the 4L60E are prety much the same tranny. GM just re designated it the 4L60 (non eletronic shift) ,then came the 4L60E (eletronic shift).
4= 4 speed
L= lock up
60= capasity 60,000lb (combination of vehicle weight and towing capacity i belive)
E= electonic shift