What year did Ford switch from 3 bolt to 4 bolt crank balancers?

I want to find a single groove crank pulley if at all possible for my 302, but its a later model with the 4 bolt balancer. What year did Ford start using the 4 bolt instead of the 3? Anyone know a particular Ford that would have had such a pulley? Obviously a non-power, non-ac, pre-smog.

Will a pulley from other Ford engines fit the small block?

So many forums here it was hard to decide which ones to post the question.

'69 and up. Or maybe mid '69 and up 302 and 351w. Try trucks and vans for no A/C and no P/S.

Try and get all the pulleys from the same engine or they will be a big chance of them not aligning
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Good luck, for some reason junk yards love to pull the accesories off the engine and throw them in a pile. I still haven't found pulleys that line up all the way. I am using a 4 bolt balancer from an 84 302 and a pulley from an unknown engine.
[addsig]

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84 gt 460, 4 speed, all kinds of crazy sh!t, 5-lug, 4 wheel discs

<font size=-1>[ This Message was edited by: sevenlitrestang on 10/28/06 9:39pm ]</font>

My '69 351W has a 3-bolt pulley. Maybe it was a mid-year change or something.

69-70 is when it happened. Yeah, get all the brackets/accessories you can from a complete motor and use them. Ford had so many different offset and diameter pulleys back then. You will burn up lots of time searching for individual parts/pulley/brackets/etc.