If you're talking about P/N 8501, it is just a parts swap. I ran one for a few years on a mild SBC with no complaints. Picked it up after having some high rpm misfires related to a few (poor quality) ignition modules.

 

The MSD HEI module is a little tougher to get in and out of the ditributor body, I found it necessary to remove the distributor from the engine to mount it properly. In that respect you will have to re-set the timing when you re-install it. I wouldn't expect it to change anything else though.

I went with the matching MSD coil and was impressed with the increased spark output - especially at higher RPM.