Personally, I would find one with the 4.6. The motor is better suited for the weight of the car, and the gas mileage is not that much different.
The V6 does have the head gasket issue, and struggles to climb hills on the hwy.
97 T-Bird LX 4.6 - 80k miles
94 Supra TT Auto - street/strip car
04 CVPI- Brenda's car - 76k miles
95 T-Bird LX 4.6 - fully optioned, owned 15 years, 220k miles
96 Cougar XR-7 4.6- Brenda's car, owned 11 years, 187k miles
88 T-Bird 3.8 - first T-Bird, owned 5 years, 206k miles