Re: 38 weber jets size
A 38DGAS has around 380-390cfm so slightly higher than the 350 Holley. They are really easy to tune up for a given motor, apparently a mild tune pinto should run ok with V6 Capri jet settings, we used to just bolt them on back in the 90s !
My van had a 38dgas and it was only stock cam and valves but raised compression to approx 10.9 , I fiddled with jets(160) n tubes, idlers etc till it was running smooth. Yours is a half up cam so it'll not have a smooth idle and that's where the fuel/air mix is most inefficient. If you car tries to hunt or jolt at normal speeds ( continuous cruising at low revs) it is way too rich.
Getting back to Holley's, the old trick was to run a metering block from a 650 or 750, and weaken the power valve spring, well this is what we done with a 465 on pinto, then realized the whole thing was rubbish and went to 2x 40dcoe !