The 3rd generation GM six.

[shp4man]

My truck had a 250 CID engine when I acquired it. Turns out it was an old rebuilt engine by a local company (Jasper). Figured that out when I took the valve cover off for a reseal. Clean as a whistle inside.
It had some ignition and carburetor issues, as you would expect, but those have been addressed.
Anyway, it keeps up with modern traffic pretty well, uses no oil, and is completely reliable. I'd drive it across the country, no problem.
Alls I'm sayin' is don't trash the old six unless you're a drag racer or something. It's a damn good engine.

[Warrens69GMC]

I have a 250 from a 1979 nova non-integral head and a 1980 292 sitting under a carport.

[AcampoDave]

I read an article in the Hagerty news lettler titled "It's more fun to drive a slow car fast than a fast car slow" (or something like that). It really summed up how I feel.... things like nailing the downshift in a turn, slamming the pedal to the floor as you summit a hill, winding the motor up to its sweet spot... all that stuff can be done as you keep up with modern traffic. Meanwhile a high output ride stuck behind a Prius is hardly living up to its potential. People like to trash small engines, but when they are tuned up and running like the proverbial "well oiled machine" that they are...they can be a blast to drive. Especially with a manual transmission.

[The Rocknrod]

Shoot I had a 235 in my chopped panel with a Saginaw four speed, it was kind of a dog until I had the infamous Steve Secor In Rancho Bernardo, CA tune it up, rebuilt the dual Rochester carbs etc. It was a little hot rod after that. I guess Steve's son took over the business though so that resource is history. Steve used to race these straight sixes.

[TJ's Chevy]

Inline 6's to this day are still doing the hard work in this country while v8's are keeping me employed. V8 diesels that is.