There's also the Compufire DIS-IX:
Click to view attachmentMost of those other alternatives are just points replacement modules or improved distributors. The DIS-IX is real direct ignition and throws a helluva big spark. It isn't crankfire, uses the 009 distributor as the trigger. I gave that engine to my son and it's still throwing big blue sparks six years later. Except for the 009 advance curve (I actually used a 010) it works great. Needs special wires (comes in the kit) and a wider plug gap. About 300 bucks.
I've also used an Electromotive HPX crankfire, but not on a VW engine. Electromotive does have trigger wheels for VW's (914's) though. I've also bought one of the Megajolt Lite Jr. kits, which uses cheap and easy to find Ford EDIS parts, but haven't put it together yet. Of all the alternatives it seems it will be the best, with a provision for vacuum advance and fully programmable advance curve. Good stuff, better, more modern, and lots cheaper than any of the other alternatives listed. No question about the dependability of the Ford parts, maybe some questions about my soldering abilities.