OP I would very carefully check the requirements 60601 is calling for. Are they cut'n'pasting old test values from 7637-2 or just calling it out, "to meet 7637-2" and how old is all of this?
ISO 7637-2:2004
"The test levels reflect the situation of load dump at generator rated speed. If a central load dump protection is used, apply test pulse 5b as defined in Figure 12 and use the values in Table 10." {customer specified}
ISO 7637-2:2011
"The test pulses 4, 5a, and 5b have been removed from this edition of this part of ISO 7637, since they are specified in ISO 16750-2 and ISO 21848."
It's a 24V system? Either 151-202V pulse OR 65V with alternators having zeners. 174V is a brutal single pulse like 13kW TVS if you hard-clamp it. Test Pulse 1 is -600V, Test Pulse 3 is -200V for severity IV.
The LT4356 is for a clamped alternator 80V max. and milder transients. Not suitable for road vehicles and big trucks 24V systems in my experience, even with decent design enhancements. The
-3 datasheet has more design details, and there is new
LTC4381 datasheet does better discuss the mosfet requirements (even though the part has a smaller internal mosfet). But dropping 150V while flowing a few amps
Is it permissible for the product to reboot or blow a fuse with load dump, or does it need to operate like nothing happened?
I would not jump to solution just yet (engineers love to do that) but instead look at the detailed requirements.
The trap trifecta is operating during cranking (4V/12 power), taking high voltage -ve spikes, and either ride-through or switch off during a load dump.
If you design an SMPS with high input voltage say 75V, then clamping transients up there is much less costly. Or an intermediate DC bus that can be dual-fed from a extra boost-converter to keep the product running during cranking. You also need big capacitance for hold-time to cover the other pulse tests for switching transients.
Motorized fire engine siren Federal Signal
Q-Siren operating current is 100A/12V, so imagine that much load switching on and off but it's less than that heater. Federal also makes all the light bars and solid-state sirens for cop cars emergency vehicles etc. which look reasonable at 20A Class-D and LED's only a few amps. Note Federal says nothing about transient rating or protection in their vehicle products specs.