as I understand, the accelerator pumps, as well as needle and seats, are interchangeable.
as far as the base, that can be changed out also.
I know of a Darrin that ran around with a 4-cly. carb for years before I sent him a 6 cyl one--note--it ran around for years!!!
I have run my 161 F-head HJ with a 161 L-head carb, then changed to a F-head carb and could not tell the difference.
bottom line is that to say it will not work on a Darrin is crap==I do not claim that it is an except replacement, but it would surely run the car down the road, or at least to and from the trailer for the wusses than do not drive them at all!!