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

AJ/FormS said
mph
According to that same #40 bulletin, your 400hp, 273 auto, has a w/p of 2900/400=7.25, and should go a minimum of 120 in the qtr @ about 11.1 sec; all with a race chassis. A stick car, in the late 70s would have gone 2 mph faster and possibly dip into the 10s.
A 400hp,NA, 273 would be very special indeed. That's about 1.46hp/cid, and it's running in; very hot street360 or supercharged territory.
Sweet!

So how about telling us a little more about the build? Ima gonna guess your cam has an ICA of 80* or better?

The hp per cubic inch is harder to get from larger engines not smaller engines. The main down fall for the 273 is bore size but takes ford's 289 same 4" bore as 302/351/400 and can take any head as them so air flow is no problem and rpm becomes the only limit. If build with the same quality of parts in the rotating assembly the smaller engine (with same bore size) can always reach the rpm (piston speed) to equal the hp of larger engine as long as the valve train is up to it.

Now 273 the problem is bore size and how much air flow you can get out of heads in that tiny bore since no one has flow Mopar heads on anything but 4" plus bores it hard to say I've seen some 305 vs 350 comparison and the losses were less than 10 cfm with 1.94 valves.
I'd say someone with a Nascar budget and some raw W8's might get some crazy hp numbers but for us ported EQ's might get us to mid 400's depending how much the notched bore eats up flow wise and can stay in the sub 8000 rpm range.

As for the OP these 273's are way under geared to get any decent times.