Alternator brackets, A/C or no A/C

I am finding a large mix of alternator brackets were used over the years. some are designated for A/C, others are not. Does it really make a difference?

I am using the top one below. I guess it is a non A/C bracket, even though it was on the 78 motor home 440 that had a single belt A/C. I am using a Sanden two belt compressor with a 2 belt pulley on the alternator, using both belts.

The bottom picture below is designated as an A/C bracket. It looks like it has more support with an extra mounting location to the block.

Should I switch over to it being I am using A/C and two belts?

The top triangle bracket will not work with a two pulley system. The bottom bracket was used on factory AC cars. To accommodate two belts the alternator was moved closed to the engine block and the belts were routed at a higher angle to the compressor pulley. I believe a non AC bracket and single pulley alt would line up with the outer pulley on the sandon compressor.

I have been installing Vintage Air on my '64 Polara, and have been down the road on A/C brackets. That lower alternator bracket actually bolts to upper motor mount ear on the block. To use it, you need an idler pulley and bracket, plus spacer. Classic Industries sells these as MP600170 and MP700216. You will also need a 4-groove crank pulley and small diameter water pump pulley that A/C cars had. There is also a small alternator bracket required; Classic Industries sells it as MD2421. The front groove of crank pulley runs water pump through idler pulley. Second groove runs power steering pump. Last two grooves run alternator and compressor.

Bouchillon sells all the brackets and pulleys needed to convert to AC. If you are running a power steering pump you won't need an idler pulley.