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

Here's my 273 combo:
OPTIONS:
273 V8 (122K miles)
4.10 sure grip rear,
Edelbrock RPM intake,
Holley 600cfm double pumper,
.515 / .525 Lunati Camshaft
port & polished factory heads,
V-Force Dual exhaust,
factory 4 speed,
around 285-300hp
Feels like a low 14 sec or maybe I can break into the high 13's if I launch her just right!
I've been told a set of headers would really wake her up! Seriously considering it, just wondering if the dollars put out will give me a significant HP boost like 40+ more HPs!