On May 17th, I ordered a set of Clevite 178P-10 main bearings. The expected Shipping date was June 8th. Now, the shipping date has been moved back to July 29th. The bearings are supposed to be shipped from Clevite. On the other hand, Sealed Power M-Series bearings are in stock, and they are cheaper. 

Based on reviews, I gather that the Clevite P-Series bearings are superior to the Sealed Power M-Series, but I can't confirm it. I'm willing to wait for better bearings, but who knows how much time I have left at my age. I suppose there's always a chance that the expected Shipping date could change either way. 

Recommendations?