Manual to power steering conversion?

[berghandler]

My grandson and I are trying to convert a 1972 C10 2WD from manual steering to power steering. I have a 1969 C10 with power steering on it and am using it for a blueprint. I have removed the single sheave pulley from the crank end on the 1972 C10 and trying to find a 3 sheave pulley to replace with. I have found a couple aftermarket pulleys but the bolt mounting circle pattern is not the same. Our single sheave pulley had a 3 1/4" BC and the aftermarket pulleys have a 2 3/4" BC. Any ideas why. I have tried at least half a dozen online parts houses but no luck. I'm not sure if the water pump is a low profile or high profile water pump but apparently it matters also, so I need to know how to recognize that to be sure I get correct crank pulley for this power steering conversion.

Thanks

[Accelo]

A few questions so we can be of assistance;
Why the three sheave pulley? Does the truck have air?
I have a couple of pulleys that came off a stock 70 with air I can post pictures of.
Are you using the cast iron truck only pulley as a pattern on the 1969 truck?

[geezer#99]

Might I add that your motor in the 72 might not be original. Could be an older 283, 307 or 327. Different size pulleys on them.
Easy to tell short or long pump. You call them low and high pump. Same thing.
Short pump only has about 1/4 inch between pump and timing cover.

[berghandler]

Reason for 3 sheave pulley is because it does have air but also on my 69 the v belt closest to the radiator, lines up perfectly with the power steering pump thus a straight shot for the v belt, even though the air isn't working.

[berghandler]

Also aftermarket pulley is sold saying it will fit all size GM motors of that year.

[berghandler]

I should also explain that the power steering total package that is on my 69 used to be on this 72. I did a complete swap to make the 69 power and the 72 manual years ago and everything fit both ways on the swap. So now I'v gotten the 72 restored and running and would like to have both with power steering. but cannot find a 3 sheave pulley in an aftermarket with proper bolt circle even though I've already done this to the 69. So not sure why?

[kwmech]

With the short water pump, the closest pulley to the crank is the alt. 2nd one out is for AC and the 3rd is for PS. I've never seen it any other way from the factory

[72BBGMC]

You need a 2 groove pulley for the alt and ac, and a single groove ps driver pulley. The driver pulley bolts on top of the first crank pulley to give you 3 grooves. The 2 groove pulley is GM p/n 3744043 and the ps driver is GM p/n 3751232. If you are interested, I would take $40 for the pair plus $10 shipping. The ps pulley has 2 spots that look like pits, i'm not sure how these got here, the pulleys were an inch deep in grease. I don't believe the small pits will hurt anything since they were running like this.
Hope this will help you figure out what you need.

[El Dorado Jim]

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