Opinion on Clifford mods for Slant 6 motors

No way... not even close. I built something similar in my Yellow Duster without using Clifford items.

I would say it was between 200-225 hp. Milled the head, Megasquirt TBI, cast iron exhaust manifold, Erson 270 cam, 3.73 Gears, home port job. Best time was high 15's, driver skill could be improved.

My suggestion is to home rebuild the bottom end, get the heads gone through (Mill, Seats, 3 Angle). Purchase the Aussie Hurricane intake manifold, Oregon Cam Grinders (Regrind), and only purchase Clifford Headers.

Results will vary.