I have run stock and aftermarket HEI on the street and circle track with no problems. Cheap and easy to find spare parts in a pinch.
Is it worth it to use something like an MSD-6AL and MSD billet distributor on a 400hp street engine?

Just trying to weigh the pros & cons for the added expense.
Does anyone have a true back to back dyno or 1/4 mile time to compare?

 

The box helps if you plan on using n2o but if not, just keep the HEI. Finding a good place to mount the box can be hard. My Digital-6 box is mounted on the passenger floor, under the floor mat. It's actually a pretty good spot, just gives the passengers less foot room though. Boxes are noisey too, which is annoying, which is also why I put a floor mat over it... to reduce noise.

 

box is great for spray or boost. not much difference on a na engine over a properly set up hei.

 

A 400 HP engine running WOT at a 12.5:1 AFR and only up to 6000 RPM will probably run exactly the same with either the MSD or stock HEI.

If you tune the WOT AFR to 13.5:1 or leaner (power-tuning), or go much above 6000 RPM for any amount of time (dirt racing), then you are likely to see the MSD clearly come out on top.

The MSD will also allow you to run WOT with an AFR of 10.0:1 and lower, if that's what you want or need.

An engine only needs enough spark for proper ignition.
What it takes for proper ignition depends on conditions in the chamber.

 

the lower-level MSD boxes are a gimmick at best. They do absolutely nothing but add another link to the things that can fail within your ignition system.