Just how quick were the 273 Commando's in the Quarter-Mile.

I have posted this before but to answer the capabilities of a street legal 1965 Plymouth Valiant 273 in the period 1975-1980 in my case was a best ET of 12.72 @ 108 mph at Fremont Raceway, CA
I built the motor at my Community College auto technology class:

All bearing and piston ring clearances set to maximum allowable factory specifications. Reciprocating assembly balanced.
Stock block bored .060 over to 282 CID with deck surfaces cleaned up by machining.
Stock connecting rods (beams polished, shot-peened, aftermarket rod bolts)
Forged steel crankshaft (was told it was for a 318 truck, but may have been stock 273)
TRW domed forged aluminum commando pistons (notches deepened with tool for valve clearance) 10:5 to 1 (advertised)
340 windage tray, melling high volume oil pump, stock oil pan lowered two inches
Stock cylinder heads w/steel shim gskt (ports matched to gaskets with dremel tool and deck surfaces machined)
stock valves polished
Stock iron rocker arms with aluminum valve retainers and aftermarket pushrods and locks, dual valve springs, teflon seals
Iskendarian 1012C solid cam 312 degrees advertised @ .580 lift
Edelbrock 340 TM5 Tarantula aluminum intake manifold with 600 CFM double pumper Holley
Holley electric fuel pump, pressure regulator, aluminum cool can (ice)
Mopar add-on electronic ignition, total advance 35 degrees, Packard 440 wires, Rajah clips
Cyclone fenderwell headers (unequal length)
Mopar close ratio A833 four speed (prepared by Pepe Estrada) with performance clutch and 30# steel flywheel, Hurst shifter with "T" handle
Lakewood scattershield and driveshaft loop, pinion snubber, Super Stock leaf springs
Solid steel motor mounts, frame connectors, driveshaft loop, SS rear shocks
M & H 10 inch wide slicks (ten pounds pressure), 26 " tall, black steel rims w/rim screws
Centerline front rims with 15" VW tires
1970 Dodge Challenger 8 3/4 rear end with 4.56 sure grip

Vehicle weighed 2960# (manual steering and brakes)
One brief water burnout in second gear.
Clutched engaged at green light at 6000 RPM, full power shifts at 6000 RPM, trap 6400 RPM and still pulling strong past finish line.

P.S. Orange flex-a-lite fan, firewall brace (to eliminate flex from heavy duty pressure plate), trunk mounted battery, velocity stack, heat crossover blocked with liquid steel (however, the liquid steel eventually began to break up). Thanks to 69 CUDA 440 for reminding me what I had done but left off the above list.