There are a couple of different fuel injected B20 motors.
There are B20 motors with K-jet and with D-jet, and there
are B20 motors with more or less compression.

All FI B20 motors have bigger valves than the carbed
versions. This is good. I've read that the earliest B20
fuel injected motors were well ported and that later
versions the valves were more shrouded. I'm not even
100% sure what this all means.

I think for the best power, you should go for any B20
with D-jet injector ports. If you can find one from a
1970 1800 or 1971 142e, all the better, but mostly any
d-jet B20 will be good. If it is an F motor, it will
have less compression than the E version. This is really
just a matter of skimming material off of the head until
the combustion chamber is smaller. With modern crap
gasoline, I think you're better off with 9-9.5 to one
compression rations, unlike the 10 or higher that you'll
get with a B20E.

In other words, any d-jet head is good enough. If you
get a d-jet head with lower compression ratio, just skim
it until it has the B20E ratio and you're good to go.
chris