Which brand of rod & main bearings?

Clevite 77 P-series were not original equipment to my knowledge. AMC used Federal Mogul bearings that were "sintered copper-lead alloy" and date stamped. 

Clevite 77 P-series is just the most popular brand of tri-metal copper bearings. Lots of other manufacturers make tri-metal copper bearings, though maybe not for AMC. Tri-metal copper bearings are a heavy duty type of bearing that can withstand very high bearing loads, but have a relatively short service life because the bearing surface is so thin. They are a good choice for an engine that will see a lot of hard use like towing or racing, but is not expected to last much more than 100,000 miles. 

King only makes bi-metal aluminum bearings for AMC engines. Their connecting rod bearings are King's SI-series and their main bearings are King's AM-series. Both are bi-metal aluminum, but the SI-series contains more silicon which makes them harder, more durable, longer lasting, and gives then a higher load capacity. Bi-metal aluminum bearings cannot withstand bearing loads as high as tri-metal copper can, but they are harder and thicker, so they last much longer. They are also more tolerant of slightly worn or irregular crankshaft surfaces. They are a good choice for a stock or mild engine used under average or favorable conditions where long service life is a goal. 

The only benefit tri-metal copper bearings like Clevite 77 have over bi-metal aluminum bearings like King AM and SI is increased load capacity. That only benefits you if your engine NEEDS higher load capacity, otherwise it's a waste. King's SI bearings have nearly the same load capacity as Clevite 77, and King AM bearings are only a little behind that. You should know that the vast majority of modern production engines come with bi-metal aluminum bearings as original equipment, including many heavy duty Diesels. Bi-metal aluminum bearings are also vastly superior in situation where there is insufficient lubrication. A tri-metal bearing will toast itself, but a bi-metal aluminum bearing will keep going much longer. 

You can probably tell that I have King bearings in everything I own...but my engines are stock and I want them to last 200,000 miles. If you are building a race engine, they might not be the best choice. 

 

On the last 360 I built I bought both Clevite 77 P-series and King AM, SI bearings to compare them and decide which ones I wanted to actually install. 

The King looked like they were much better quality...if looks mean anything. How they look doesn't necessarily represent how they work, but the King bearings looked much better.

You're going to be fine either way.

Thanks, Scott