Group 31 Truck batteries are the same internally as Marine "deep cycle" batteries. The Marine and truck batteries are dual purpose in that they crank the engine and can handle low amp draws, as with a trolling motor, Espar heater and 12-volt (not 120 volt) electric blankets. So if you have multiple truck batteries, you can get away with using small inverters and some 12-volt appliances like electric blankets.
If you have a single truck battery, or are in a van, forget it. Use a separate, isolated auxiliary or house bank for everything other than starting the engine, and use the cranking battery for nothing other than cranking the engine.
12 volt electric blankets will draw about 4.5 amps. Over 10 hours that's 45 amps drawn from the battery. When it's really cold, batteries have fewer cold cranking amps to begin with. Drawing 45 amps out of a battery which is near zero degrees will reduce the CCA by well over 100 amps. The last thing you want to do is reduce that even further by drawing the battery down just when you need the most CCA you can get.
CCA (Cold Cranking Amps) is a rating for the number of amps a new, fully charged battery can deliver at 0° Fahrenheit for 30 seconds, while maintaining a voltage of at least 7.2 volts, for a 12 volt battery (1.2 volts per cell). The higher the CCA rating, the greater the starting power of the battery.The cranking voltage will start out at 12.8 volts, but will quickly drop to 7.2 volts within 30 seconds, to the point where the battery is depleted.
MCA or CA (Marine Cranking Amps or Cranking Amps) is the same exact rating as the CCA, except MCA and CA is for 32° Fahrenheit.
Cranking Batteries might be rated at 500 to 1200 CCA. Few engines will actually require that many amps to start, and even fewer will require that many amps for a full 30 seconds to start. Some big trucks will, tho, and it's why many of them have several batteries. But with van, a couple hundred amps for a second or two is all that's needed to crank the engine. 200 amps for 2 seconds is about 7 amp hours drawn from the battery, which the alternator's charging system will quickly put back into the cranking battery (takes about 15 minutes on average).
Cranking batteries are designed to provide very high amp draws of for a very short period of time. They cannot handle low amp draws for sustained periods, or high amp draws (microwave) for more than a few seconds.
Hybrid (marine deep cycle) batteries are designed to provide cranking amps and can handle low amp draws for sustained periods. They cannot handle high amp draws for more than a few minutes.
Deep Cycle batteries can provide enough amps to crank an engine, but will provide fewer CCA and MCA than a similarly-sized cranking battery. They can handle both high and low amp draws for sustained periods. Some (gel batteries) can routinely handle very deep discharges (20% DoD) without heading for an early grave, while others (AGM and wet cell) will last considerably longer if discharged only to 50% DoD or less between charges.
So the three basic types of batteries, Cranking, Hybrid and Deep Cycle, are all designed for different purposes. All perform exceedingly well when used for the purpose they are designed for, and all perform badly when used for something they are not designed for.