Trying to calculate E/T

You need to be more specific about the car in question, if you want an accurate answer.

Here are the SHIPPING WEIGHTS for '68 Barracudas from the Stanard Catalog of American cars, a reference book that's a pretty good source of info like this.

Street-ready, with gas, oil and water, plus undercoating and accessories will usually add about 250 pounds to shipping weights, so keep that in mind. Your car won't be anywhere near as light as these quoted weights.

1969 Plymouth Barracuda:
Notchback coupe /6: 2,715 V8 2,910
Fastback /6: 2,810 V8 3,005
Convertuble /6: 2,870 V8 3,070

A Formula "S" 340 car would be heavier than these weights, by probably 150-200 pounds because of the extra weight from the dual exhaust system, the 727 vs. 904 transmission (if it's an automatic) and the 8.75" rear axle assembly (vs. the 7.25")

Lots of variables... A/C and P/S can add over 100 pounds, easily...

So, you need to tell us EXACTLY what you have before we can venture a guess. Even then, you need to take it to a certified scale and weigh it so you'll know, for sure.

I'd try a guess, but I have no idea what body style it is, and you can see, looking at the shipping weights, how much difference that can make.

Try us again... with more info!