I have 1984 350 4-bolt that i am rebiulding. My problem is that with my new summit double roller timing chain set the back of the chain rubs on the oil gallery upstands it hits by approx 1.5mm. Wats the best thing to do?? grinding/machining or spacers...

Grind the boss of the block, it shouldn't take too much.

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That's a pretty common prob. Simple fix, just grind the boss down till you have clearance.