vintage tongue in cheek . . . but only for a moment . . .
An Atlas I6 should make that '68 scoot - might even give a period vee-thingie a run for their money . . . it's probably a bit lighter then the 250. . . . taking the car into the 10-11 pounds per HP zone.
And an LL8 is still in line . . . so it's got my vote over a bent eight crate motor any day. . .