Don't know why the parts guy couldn't find the listing .
Could be a problem with the year, because the 440-3 in 79 was a hold over from 78 and the 440-1 was no longer available in the passenger vehicles/ light trucks.
I had tried to order a 79, 1/2 ton 4X4, with a 440, and ended up with a 360, 4BBL.
Any how Fram filter P/N's are PH-43 the short filter ( 4" ) and PH-8A the longer ( 6 " ), high volume .
Main reason for the shorter filter was clearance to the fan belts, and rad fan shroud.
Interesting little bit of Chrysler history , involving MH chassis.
Mid 80's Chrysler was sued, because they had , over produced the 78/79 MH chassis , and re-serial numbered the chassis as 80 & 81 when they were sold to the MH manufacturers. So as is apparent in your 81 on a 79 chassis , the chassis was sitting for 2 years before it was built on.
For more on the 440-3 you can visit this site.
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