This is the pulley I designed around, and it's fairly common. I've also seen it on '92 & '93 gas trucks, and others. The original-size 90x30x17mm pulley 12556504 is probably equivalent to ACDelco 38020 (
Gates 38020) &/or
ACDelco 36299. This one (smaller than the original dual-alt idler, but the same as the original single-alt idler) might be Dayco
38007 or 38006. The spacer is not used for tensioners, but it's required for idlers and for this mod. Some bolts are 10mmx1.5 with a 13mm head, but others are 12mmx1.75 with a 15mm head & a matching spacer.
Turns out this bolt is actually 12mm. An earlier one I checked was 10mm, and I didn't realize this one was different when I added that text.
![idler.jpg This is the pulley I designed around, and it's fairly common. I've also seen it on '92 & '93 gas trucks, and others. The original-size 90x30x17mm pulley 12556504 is probably equivalent to ACDelco 38020 ([url=https://www.amazon.com/dp/B000C2SGW0]Gates 38020[/url]) &/or [url=https://www.amazon.com/dp/B002E54VSG]ACDelco 36299[/url]. This one (smaller than the original dual-alt idler, but the same as the original single-alt idler) might be Dayco [url=https://www.amazon.com/dp/B000C0YR1G]38007[/url] or 38006. The spacer is not used for tensioners, but it's required for idlers and for this mod. Some bolts are 10mmx1.5 with a 13mm head, but others are 12mmx1.75 with a 15mm head & a matching spacer.
Turns out this bolt is actually 12mm. An earlier one I checked was 10mm, and I didn't realize this one was different when I added that text.](https://www.supermotors.net/getfile/947195/fullsize/idler.jpg)