If you have the standard Pierburg fuel pump you probably will not need the
fuel pressure regulator. I put one on my B20 powered 122 in days of mystery
carburetor problems a couple winters ago and after a few months the regulator's
diaphragm let go, pouring gasoline all over my engine and generator.
Fortunately I recognized the problem and when I installed it had left enough
hose that I could just take it off and rehook the hose to the front carb.
Later I checked the Pierburg's output under several different conditions and
speeds up to about 6 grand, and it was always exactly 3 psig, exactly what the
SU carbs need. I found earlier that if I set the regulator pressure to 2.5
the car would go OK for a few blocks and then begin to starve, so as nearly as
I can tell, the regulator was a pimple on the backside of progress.

BTW it was NOT an el cheapo regulator - it was name brand. Same kind IPD
used to sell, although I did not get it from IPD.

Enjoy those dual carbs!
--
George Downs, The "original" Walrus3, Bartlesville, Oklahoma