The 4.6 SOHC is well known to be reliable beyond 300,000 if simple maintenance is performed (oil/coolant changes).
The 180,000 mile Explorer motor I am putting in still has visible cross hatching in the cylinder bores.
Use good oil, 5w30 or 0w30. Change it often so it doesn't sludge up, and the motor will be fine.
Want more power, PI swap it, port the heads, get aftermarket cams and headers and you'll have plenty of power.
If you want top end, 4v heads, or swap in a block from a Mark VIII to save yourself 80lbs.
97 Thunderbird LX (The GT Bird)
PI Swapped NPI motor with some port work on the heads, PI cams, 80mm MAF, CAI that feeds from fenderwell. Jmod, 3.73:1 TL in Mark VIII carrier, Mark VIII aluminum LCAs, 93 Mark VIII driveshaft, PBR brakes (soon to be Cobras), 18x9 wheels, 255/40/ZR18 Tires, Front and Rear strut/shock bracing, GR-2 shocks, Eibach 1.5" springs, 1989 SC front and rear sway bars.