I too have the 3.0 but it is in a 2 door. Before I lifted and put on bigger tires I was running constant on the open road around 75. One trip I took I sustained 90 no problem. That was when the truck had 170k on it. Now it has about 210k with the only engine work being done since then is valve guide seals.

89 2dr 3.0 AT, manual hubs. 33x12.5 MT
gen 2 coils,Cranked front tbars
Dons rocker protection, Front/Rear Bumpers. ARB rear locker, 2" BL, Beefed up skid plates/trailing arms. Gen II uca, 2 Bouncy seats www.youtube.com/TagGeorge