There was a recent thread (sensibly closed at the request of the OP), regarding EV1 vs. EV6 injectors, that contained some misinformation as to which is which, and what's what.
The difference between the EV1 and EV6 units is not the electrical connection, but rather the physical size and internal design of the injectors.
This is from the FRPP catalog:
Between these the EV6 is more desirable as it has quicker action (the pintle has less mass, and the coil saturates and de-saturates more quickly/cleanly). The EV6 also has a 4 or 6 "nozzle" spray pattern for improve atomisation of the fuel.
The '99 to '04 GTs came from the factory with EV1 injectors, with the Jetronic/Minitimer style connector.
Here are the injectors offered by FRPP, you can see that both the EV1 and EV6 can be had with either connector--the EV14 is yet another evolution of the design.
For the OP of the other thread, if the 39lb/h EV6s will supply enough fuel I would select them (with connection adapters) over the 42lb/h EV1s.
Here's a link to the full FRPP Fuel Injectors and Adapters section
from the FRPP catalog. There's some good MAF info too, great reading...
FWIW, I just recently installed a set of the 24lb/h EV6 injectors (FRPP #M-9593-AA02, purchased from a forum brother) in my '03 GT, and after getting the AFR dialed in (I had to set the high slope to 25.16lb/h) I can report that the engine is happier with the closed loop AFR better controlled; and much more consistent (less load dependent) open loop fuel control as well.
Picked up 1/2 to 3/4 MPG as well.