I use a Pertronix II in my stockish '55 Merc. Been in there for about 10 years with no issues. 

I'm looking to upgrade my stock, 1957 Thunderbird tach-drive distributor. I'm considering Pertronix l or ll/w with Pertronix external RPM limiter, Duraspark conversion, CRT distributor/w external RPM limiter, or FBO rebuild/conversion, the latter being the most expensive. The FBO and CRT have upper and lower shaft bushings. Is the additional bushing overkill? Pertronix conversions seem to be the most common and least expensive. What are your recommendations? Ted has already said that he prefers an electronic conversion. My brother had an MSD distributor and External box on his I/O 351W, but the MSD components were expensive and not particularly reliable. Maybe they're better suited to cars, not ski boats.

Thanks