I have been VERY happy with the stock 1975 240 distributor, which has
the electronic ignition of later models in a distributor that works with
the B20. It does NOT accommodate D-jet, however, unlike the 1975 164
distributor, which is also electronic. (I will install one in my 164
as soon as I detect problems associated with the third distributor in my
69 164 𖒕K miles] but it is running so well now that I am not motivated
to do so.)

I suspect that advance curves could be tailored for specific applications
but the Bosch electronic ignition seems to be good and strong. I am using
IPD street performance cams in both B20 and B30 engines and very happy with
both. While performance could undoubtedly be improved in both, at present
I have no reason to be dissatisfied.
--
George Downs Bartlesville, Heart of the USA!