The main drawback would be the alternator. The 55 or 65 amp alternators on those cars were really poor. Their output at 800rpm is abou 20 amps. Its probably linear to max output at around 2000 rpm.
That car with normal aux fan, A/C and inside blower can take 30-40 amps. In trafic this don't cut it even without the headlights. The car can not stay up with wipers, A/C, aux fan, and headlights never mind the rear window defogger. Luckily the A/C is cooled off enough by rain that the Aux fan usually shuts down or you would soon be dead soon with the wipers.
Bosch Master, ASE Master, L1
33 years MB technician