They were a 93 Cobra engine with the GT40 Tubular manifold. The Cobra engine was rated at 240Hp but looking at the mods it had compared to the stock windsor (220hp) it probably had a little more than that, and US dyno numbers prove that .
Add the better manifold it should have been making nearly 268hp/200Kw.
Only thing would be that it was tuned for 92RON octane fuel whereas the the Cobra would have been 92MON (around 95/96RON)
Even so the EB GT should have been quicker than what the Mags ever got, the 93 Cobras have ran as quick as 13.9 in the US stock, and they're only about 150kg lighter.
Oh, and EBGT dynoed around 140kw at the wheels at the Tickford Dyno day, about the same as an ED Sprint, but the GT had over 200,000kms on it, the ED had less than 100k.
Mine dynoed 127 and it chops VN V8s