Inline-6 carb preferences?

[Oregoon]

'74 GMC 2WD LWB with a 250 and a 3OTT.

Running an HEI, totally desmogged and the stock Rochester. No emissions tests, so that's not a concern.

The truck is my daily driver, so fuel economy and performance are the goals. I haul a bit with it, though nothing outlandish. Lumber, hay, crates of vegetables. Mostly, I cruise around Portland with it. Top-end is not a concern. I chill in the right lane and prefer backroads.

Considering a header, new intake (if needed!), and a carb. Maybe a Carter YF with a manual choke? The Rochester is tempermental and I'd like better economy if I can attain it. Best I've got is 20, but usually I get about 15-17.

Open to any suggestion. Not sure the 4bbl route is really worth it. I'd prefer a 2bbl progressive, though I have really enjoyed the Carters I've owned on Ford-sixes. Very simple, very reliable.

Educate me!