I am finishing the re-assembly on my LT-1 350 for a '71 Zed , the engine is std bore with 12.5 TRW pistons , pink rods , steel crank and a crane roller cam , 3 of the roller lifters were rusted / pitted from improper storage so I bought 2 sets of lifter pairs , part # 11515-02 ( the complete kit would be 11515-16 ) the original lifters have a necked down area just above the roller , but the new ones I have bought are necked down a bit ,but not near as much as the originals , I have looked up the lifters on ebay and see about 4 differant sets and the pics show that the ones in the auctions are exactly the same as my originals , and not like the replacements I bought, has anyone run into this before ? I would think there might be a slight weight differance between them , would this cause a problem at 7800 RPM ? would Crane have built lifters themselves or farmed them out to differant venders ? any opinions would be appreciated . Thanks