...The #6454 that is right for my car, and is on the car, has 1 1/2" primaries. It's not the one that came on the car as all I got was a shortblock when I pulled the car out of the wrecking yard, but the number's are right. Per the info that Gary Lewallen (aka Vaanth) put on the internet, some of the '73 340 cars had TQ's with 1 1/2" primaries (specifically #6339 and 6340 for the CA cars) and most '74 360 cars had 1 1/2" primaries (#6452, 6453, 6454, 6455, 6488, 9002 and 9004). There appears to some '74 non HP motors that came with small primaries (#9013 and 9022), but it appears that all HP 360's had the large primary TQ's. I could be missing something, but I'm 99% certain my '74 360 did come with 1 1/2" primaries.
