This is just an example at random but I would have gone for a distributor with the magnetic pickup not the three wire connector.
In fact I plan on ditching my HEI/MSD box for an MSD/MSD box setup, separate coil.
As for selling it to you, they assume you have informed yourself but mostly Iīd suspect itīs money in their pocket above everything else.
Did you ask for tech advise from the man who sold it to you ?