I think they dont make a larger group size. 123 takes group size 46 or 47 one of the two I am not sure.

How expensive are these batteries. If you dont have too many after market accessaries on your car, you might be just spending too much for no good reason.
Remember, diesel engines need power to start only, a good alternator will sufficiently provide for all other power later.

Just my 2 cents.

MVK

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One penny saved is three penny earned.

1985 300D Turbo 179,000miles