Single or double?

shep76 said

Are there any negatives to just using an older water pump? The cast iron ones are fairly reasonable in price. Is it just the timing marks that are the issue?

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The '69 and earlier cast iron pumps are shorter and require pulleys and alternator brackets that are compatible. And finding '69 and earlier pulleys is a challenge. The aftermarket tends to cater to the '70 and up aluminum water pump and pulleys that are compatible with that pumps offset. Unless you are die hard has to be correct for that year you save a lot of head aches staying with aluminum water pump and the '70 and up pulley offsets.

As for AC the '69 and earlier cast iron water pumps ran a single belt from AC to crank. '70 and up ran a double belt that wrapped around crank, AC, and alternator.

So its not a one size fits all. There is '69 and earlier cast iron and pulleys and brackets matched to that offset. Then in '70 aluminum water pump all the pulleys and bracket offsets changed and belt routing changed to. '70 up much easier to find correct pulleys brackets ect then the earlier cast iron water pumps setups.