Aluminum is lighter and stays purty. The plastic reservoirs don't leak like many experience w/ the old cast-iron ones. They also have a level sensor you can wire to your dash lamp. I use an MC for a 95-99 Breeze w/ ABS (7/8" ID bore) on all 3 of my 60's Mopars. I had to buy a 4-2 bolt adapter plate ($30), except on my 65 Dart where I used the Breeze booster (see avatar). The first one I got cheap at the junkyard, and bought the others new on ebay for ~$25 ea, plus a spare for the shelf. A late 80's Dodge truck MC is used by many, and same PN sold in sometimes pricey upgrade kits.
