I have run my 68 charger for 3 years with toyota alternators. I burned one up and had to buy another.

I ran an electric fuel pump, electric fan, msd, stereo, etc... and still had problems with good idle voltage. Everything would be fine until I turned on the A/C which would automatically turn on the electric fan.

At speed I was fine but not at idle.

I installed a powermaster 140 amp gm style alt. 90 at idle. Which is what I installed 4 years ago on my 67 Coronet which has a bigger mercedes electic fan and msd atomic system and fuel pump plus A/C. Never had any inkling of a voltage problem.

While the toyota alternators worked ok they were always working hard which isn't good for the life span.

Using a higher amp alternator with an easy duty cycle or load will make it last longer.