T5 Into An 03 Gt, How Difficult?

I think the G-force T-5 is more adapted for the Fox body (and early SN95) Mustang. It features mechanical speedo output and bolts to a fox bellhousing that doesn't mate to the 4.6L

So to even have a chance to bolt it to an 03GT would require an adapter plate for the bellhousing (not sure if it exists) and convert the tailhousing to a electronic speedo version which will require some disassembly and you may need the late model mainshaft

Easier way might be to buy an 99-04 T-5 from a V6, but the G-force gear kit and do the upgrade yourself. You'll still need the adapter bellhousing (which unsure if it even exists)

Not really sure if this could easily be done