[66Submarine]

Yeah, I like to at least check the odometer with map distances.

I'd guess you probably just had the choke closed further than you thought you did, though. Check it again and I bet it'll be a whole lot better.

You could possibly have a 4.11 rear instead of the 3.73 most of the came with, but you should still have got a lot better mileage than that (and it seems like 99.9% of the base-model trucks came with 3.73's IME). 8MPG is 454BBC mileage!

BTW, 10 degrees advanced (obviously with the vac advance plugged and the idle slow enough that the mech advance isn't out) is what I have mine set to IIRC (might be 12).

Also, it's super-easy to drop a column-mounted tach in to see what RPM you are running at any given time if you're curious (I always like having one).