I Dyno'd my 70 Mach1 back 2 years ago.
I had Open Chamber ('1972) heads on it with forged pop-up pistons for 10.4 to 1 compression, not quite as high as a stock 70 Celveland which has 11 to1.
Also had a 750 holley Vac Sec, Edelbrock Performer dual plane intake, small Crane Cam (.510 lift), and headers.
I got 292 rwhp (5,000rpm) & 340ft lbs (3,800rpm) at the rear wheels.
I have since redone the heads with stainless valves, chenged to a Torker Single Plane intake, changed to a 650 Holley double pumper, and changed out the Cam to a Cam Research .540 lift grind, added roller rockers and a windage tray ......
Makes way more power now, but haven't dyno'd it yet.
Doesn't respond in low rpm quite as well as the old engine, but it's a 4 spd Close ratio car, so it's easy to "urge" it into the power band, which is 3,200 to 7,000rpm
If you're wondering why such a high reving set-up, I Road Race this car at an amatuer level at Tracks such as Mosport & Shannonville, TMP, etc
Clevelands Rock!
Mach1steve