I read here once about someone smearing the hose with vasoline then wrestling it on. I wouldn't go that route. Others say they've trimmed the length in order to get it on. I figure it was designed with a specific length for a reason.
That small $2 hose will require removal of the H2O pump in order to change it out. The archives are full of how-to's on the M103 water pump.
1991 300-SEL - Model 126
M103 - SOHC
James Madison - Oppressors can tyrannize only when they achieve a standing army, an enslaved press, and a disarmed populace.
Liberty Firearms Training - After years of trying to regulate California criminals with a never ending stream of gun control laws they have still not given up with the belief that if they make something a crime that criminals will miraculously start obeying the law.