I would just like to add something. I'm replacing the Heater Inlet Hose(Heater Hose #1) on my nephews car. The hose needed for the other end, the crimped end that goes to the engine is a tapered hose. It goes from 3/4s at the metal part of the hose to 5/8s at the engine. I found its part number in a different thread. Dayco B87612. Just cut to length.
Another part number for the short 5/8" to 3/4" tapered 6" heater hose is ACDelco 14006S (or 88907007). It's on a few web stores, but I didn't find it listed online for a brick-and-mortar chain. Also Gates 18080, stocked by O'Reilly.
Interchange Part Number: 88907007, 18080, 87612, 63030, 87610, 303612, 3035
Other Part Number: 64367, KM-2867, 303610
Not mentioned here is cutting off the factory clamps so you can use a normal hose clamp. The crimped OEM design might actually prolong the life, since these hoses seem to bulge around standard clamps, but it's just a normal hose underneath, once you cut through lengthwise with a hacksaw or Dremel, not nicking the metal hose, and spread the clamp open to discard it.
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The Ford OEM part# for the long S of "Hose 2" (outlet hose, the one without the cold engine lock-out switch) is F3DZ-18472-B, in stock at fordpartsgiant.com (they also have an OEM F3DZ-8005-B
radiator). Gates 18774 is the same - cut off the extra. It has other substitutes:
Acdelco 16051M
Carquest 18774
Chrysler 55056711AC
Datsun/Nissan 9241053F01
Dayco 86104
Dayco 86121
Dayco 87121
Dayco C86104
Dayco E86121
Ford E7UZ 18472 F / E7UZ18472F
Ford E9DZ 18472 E / E9DZ18472E
Ford F3DZ 18472 B / F3DZ18472B
Gates 18774
General Motors 14103584
General Motors 22551237
General Motors 22570030
General Motors 94106394
Goodyear 19689
Goodyear 63089
Honda 79722SM1010
Hyundai 9731224000
Hyundai 9731234101
Hyundai 9731238000
Hyundai 9732238000
Hyundai 9732238300
Isuzu 8941063941
Isuzu 8941229132
Kia 9732238300
Mazda AM1515261
Mitsubishi 2547221000
Mitsubishi MB298120
Mitsubishi MB332574
Mitsubishi MB527572
Mitsubishi MB527594
Mitsubishi MD009016
Napa Belts/Hose 10774
Suzuki 1787154G10
Suzuki 1787154G20
Suzuki 1787254G10
Suzuki 1787254G20
Toyota 8724512490
Toyota 8724512780
Toyota 8724517040
Toyota 8724517300
Toyota 8724590A13
Ultralast 18774
Volkswagen 321819375D
Went through the parts catalogs with the NAPA warehouse guy, and there is no exact "M" shaped hose to be had.