If the truck starts up and runs fine besides the exhaust flowing into the cooling system causing an eventual overheating, then I would figure that the bottom end is still fine and the rings are not damaged. Definitely something worth fixing. Plus, the 3.0 can take a lot of abuse. My brother drove my Raiders original engine without coolant for about 3 hours until rings welded themselves to the cylinder wall making the crank snap into 3 pieces. Yea, these things are definitely tough. <img src="/forums/images/graemlins/mrt.gif" alt="" />

Richard E
1989 Montero - Stock-ish
1989 V6 Auto Raider - 5.3 Vortech Swap.
1987 Mitsubishi Starion 2.6t, soon to be 3.5
1983 Honda XL600R