Sure you got 22mpg with that combo (don't forget that your tranny plays a huge part in your mileage game). In the late 1990's when I was going to college in NY, my 1982 GMC with the 700R4 and a reman 350 (I added a Comp Cam truck cam) was getting 19mpg back and forth on weekends from CT to NY for 3 years (about 150 miles one-way). How? Mainly OD on the tranny, but also how the engine was built to the rest of the drivetrain.
I believe you. But was your remanufactured 350 making 500 HP at the flywheel? An SBC can be easily configured to do one thing really well, it can't be easily (if at all) configured to do lots of things really well. An LSx can.
(I might actually be the exception. Maybe most "Older" people would be inclined to stay with the "Older" setup, I don't know about this part. It might be just me, but I like technology and the ability to "Modernize" it).
Hey, easy on the "old guy" stuff - I was 23 when my '68 came off the line. That poor car now has an LS3, Viper T56, Hydratech brakes, aftermarket front subframe with C5 control arms and brakes, 3 link rear suspension (built around a Ford 9"), coil overs all around, Recaro seats, GPS, Sirius radio, 7 speakers for the stereo (including a subwoofer), all electric/electronic instruments, and so on.
People like what they like regardless of age.
And with that, Merry Christmas, Happy Holidays, Happy Hanukkah, Joyful Kwanza, Happy Festivus, etc. In other words, Peace.