I have a stock 400 engine with the stock distributor and ignition. I want to retain the stock look but also the benefits of HEI. What do you guys recommend?

The Pertronix Ignitor.
It converts your stock points distributor to eloctronic. the only outward change is one extra black wire. You can add a high power coil, but its not necessary. Use the search engine here- lots of people have talked about the Ignitor, even today.

I have just installed the Pertronix on my distributor, everything fit well and as Z says, it looks stock...Have yet to fire the new engine tho but I've heard that they are a good set up hence the purchase.

Is the Petronix considered HEI?...or just electronic?

I would consider HEI as a brand name for an electronic ignition that was used by GM. Maybe someone else knows better.

No, the Pertronix is just an electronic substitute for points. I have a Unilite conversion in my stock distrib and it works great.

Thanks for the responses. A couple of more questions:

Will I get substantially more performance/benefit from an HEI system vs. a Pertronix one?
Do I need to get any additional hardware to allow my hood tach to function with the pertronix or HEI system?

Thanks.

Be Careful. I think that the GM HEI distributor will hit the firewall. Can anyone confirm this? Plus, you definately won't appear "stock" with the HEI. Anyone looking under the hood will spot the HEI from a mile away.

I have an HEI distributer in my 67 400. It doesn't hit the firewall however it does give me another issue to deal with. My PCV valve hose has to go in at a wierd angle due to the vacuum advance being in the way which causes it to not seat properly which I think is part of the problem I have in my post (crappy carb?). But my issue may not be shared by everyone with an HEI.
Mike