There are actually tons of mods you can do to Eagles:
dump in a 4.0 HO from a jeep,
change out motor mounts and dump in a V8 (I think the V8 will almost drop in - Possibly some small modding)
Do a stroker motor,
mild lifts and keep front half-shaft
extreme lifts and dump in a jeep full front axle,
Depending on lift, tires sizes galore to choose from,
a few choices in upgraded rear axles (from an explorer to some Chrysler/jeep rear ends,
several T-cases to choose from (some bolt in, some spline mods)
Some direct tranny upgrades (727, or some jeep bolt in's)
I guess it's like that old saying: Speed is just a question of money... How fast do you want to go?