That V-8 is now a 400hp clean burning monster that drives a 6-speed transmission and gets 20MPG.
I think GunsareOK was refering to the diesel conversion of the olds 350, which was truly a disaster.
Now as far as gas engines go, we had efficiency in 1969. I had a dodge 440 ci with three duces that produced 520 HP when demanded, and got 22 MPG crusing at 80 MPH. you could stand by the tailpipe of that rig as long as you wished and never inhale any undesirable substances, but five years later that became impossible when they added a catalytic polluter.
The enviro nutzies didn’t like the clean burning version.