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Have you got adjustable poly-locks on studs or fulcrum mount rockers? I think you would want adjustable poly-locks and stud mounts, and at least roller tip rockers. I ran 351W heads for several years on my 306 with no problems. I think I still have the push rods that I used and could measure the length if I can still find them.

The best bet is to get an adjustable length push rod, use a solid lifter, and find the length that keeps the roller tip right in the middle of the valve stem face when the engine is cranked over. That gives you ideal valve train geometry and best performance and least valve guide wear. You would have to order the correct length push rods after that ideal length was determined.

Rev