JCwhitney.com also sells a 2bbl adapter to work on a four bbl. If a new cam is needed, a very mild cam can be used. Very mild. Headers also make a difference, that and a decent exhaust system. The 250 can be overbored .030.
Back in the early '70's I remember stroker kits, flowed heads, pop up pistons. I remember a tri 40DCOE Weber set up.
Then, there was even a straight six following. The 240Z engine was a combination of the Chevy straight six, and the empty oiler from the Mitsubishi Zero fame. You could run that engine out of oil, and make it to somewhere to get it fixed.