Edelbrock 500 cfm vs 600 cfm

[4pilgrim4]

My pickup ride is a 78 Chev K10 350 4 bolt, 4 speed manual, 205 transfer case driving 3.73 : 1 axles. The carb is a Q-jet on top of an SP2P manifold with the divider removed. Fuel economy is good at 16 - 18 at 55 - 60 mph. The greatest use is towing a small 2500 lb fiberglass camping trailer.

The poor old Q-jet is really worn out, especially the throttle shaft holes. Min idle RPM is almost 1000.

Rather than re-bush the bores I'm considering a small 500 cfm Edelbrock or perhaps a mid size 600 cfm model as a replacement. Since I am not in the race crowd and my truck rarely sees 3000 rpm, my calculations indicate that a 500 cfm unit would be more than plenty. (I'm also aware of the engine size recommendations for the two carbs.)

Just wondering if someone has some experience in this area or knows of someone who does.