Pre 1995 cars have Buna-N or natural rubber components in their fuel systems. Some of these parts (fuel supply and return lines) can be replaced using viton tubing by the average DIYer. Pre-'95 diesel injection pumps also have internal Buna-N components (o-rings) that will be degraded by B-100; unfortunately, those parts generally aren't DIY replacable.
The better thing to do would be blend B100 with either diesel, or SVO to a maximum 20% concentration (ie B20). B20 is generally accepted as the maximum concentration of biodiesel for reliable operation in older (Buna-N, nitrile and natural rubber) vehicles.
More info
here and
here.