I am not sure if this will answer your question but....
the cb900 used a type of electronic ign however; the cb900 coil is a relatively common upgrade for the 750.
they generally work with no issues as long as the charging system is ok.
now I am not sure if your 350 system will be able to handle the additional current draw.
the 900 coild are about 3 ohm or so maybe 2.5
some additional info may be required.