360 Magnum building on an existing bottom end

New rod and main bearings would certainly be in order being the engine is 25 years old. Time is just as hard on those bearings as is an easy life.

There is acids and contaminants in the engine oil that work to degrade those bearings over time. The real question is what are the cam bearings going to look like?

If it is still available to run, an oil pressure test with a gauge will be a good thing to do to tell how tight the bearings are yet.

Bring the engine up to temp and see what the oil pressure reads at an idle, that will tell a lot.

Rock the crank back and forth and watch the distributor rotor to see how much slack is in the timing chain. That can give a clue too on the life the engine has had and how frequently the oil was changed.

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90,000 miles on this engine. Still pulled a few rod caps and one main. Bearings looked good, rear main not leaking.

So it got put back together with a new stock oil pump, fresh stock heads with the original lifters and roller cam and new roller timing chain.

Still running good to this day, got away with it on this one. Others may have had a tougher life, so you have to check them out.

Certainly what the lobes on the cam look like can tell quite a story too. Flat tappet cams will start going flat after that much time, just from normal wear.