Hard to start after sitting

1st the walls of the intake manifold dry out.
I doubt the carb bowl has dried out.
if so, an electric pump is a poor band out.

Take the air cleaner lid off, or the entire air cleaner.
Take a look at what is going on.
Work the throttle.
Is there a pump shot on the first throttle opening?
How about hte 2nd and third.
No? Then look in the bowl. is the fuel level low? Is pump intake covered?
No - then fuel level is low.
Yes - then the pump check ball or valve isn't holding

How 'bout the choke settings? Chokes are tricky to get perfect, and the automatic ones trickier - especially when not factory.

Bottom line is that if there is fuel in the bowl to the proper level then an electric pump isn't going to do a thing to help.

One more possibility. Summer fuel in winter weather. Yea. That crappy cheap winter fuel does have higher RVP to help with starting. The downside is those components when sitting evaporate out of the intake and even the bowl faster than summer mix.

All that vapor trapping stuff that started getting added in the early 70s (earlier in Calf) reduces this problem.