I have had a couple Volvo 244s which were efi . One time I had to replace a few injectors. i never had to do anything to the electrical side and have no idea how complicated it is . There was a control module I think mounted on the radiator support. I dont remember a crank trigger so it must have had a timing source in the distributor.
Interesting concept for sure . I expect it could be accomplished. You would need to be able to do some remapping of the fuel load i think since the volvo is a 2.4 litre. Hmm would just the oxygen sensor be able to correct that ? I dunno. Also have to make ports in the runners for the actual injectors. The Volvo fuel pump though it remote mounted that might be the easiest part of the conversion.