Steve
When I got my Indy Lights engine I looked at the Power Module, looked inside, saw transistors and said to myself "I don't think so" and went with a simple, straightforward modern ECU. Admittedly I was more interested in the car/engine working reliably than in originality. If you are trying to retain 'original looks' you can probably find a modern one that fits inside your existing box. That was done a lot on old Formula Atlantic cars to get rid of the (in)famous original Lucas system.
Your choice - Derek