I'm partial to the K-Jet injection over the D-jet.

You can't use a 75 B20 distributor on a D-jet system
very easily. The D-jet distributors have a pair of
switches on a cam on the shaft of the distributor; these
fire the injectors in alternating banks. The 75 B20
was K-jet only so there are no injection points
to fire the injectors. You'd have to modify your
existing housing to make it all work, or you'd have
to put a 71->73 distributor onto the car, but then
it won't be electronic injection unless you also get
one of those aftermarket kits that sits inside the
housing.

Also the D-Jet is much more sensitive to screwed up
wiring than the K-Jet. The K-Jet needs a different
fuel pump that pumps at higher pressure than the D-Jet.
The K-jet is less efficient than D-jet if both are
working perfectly and both motors are stock. If you've
modified the motor to have bigger pistons or more cam,
the K-jet will work without modification.

The K-jet is simple. It was used in every market
volvo could get away with it for as long as volvo could
get away with it. D-Jet isn't bad, but price
replacement injectors, "computers", and map sensors,
and injector points before you decide which you want to
go with.
chris