You should be able to tell which gears your running by looking at the rear end. Jack up the rear (and use jack stands!), crawl under the car from the passengers side just in front of the rear wheel. You'll find a metal tag fixed to the pumpkin if its still there. I had to spray mine off with brakeclean to read it. If the tag is still there and once you get the numbers use This Site (*) to find out what gears you have.. if they haven't been changed at some point.

My tag read:
WCZ-V2
279 6MC 930
Which decodes as an 8" rear with 2.79 gears and 28 spline axle shafts.

* http://www.fordification.com/rearends-ford02.htm

 

Or, simply open the drivers door and read the tag there

 

Or, with it lifted as stated above, spin the driveshaft one full revolutions and count the number of times the tires go around.

 

I don't think I'd rely on the little (and probably 42 year old) rod bolts for anything past 5500, tops. Even if the rest of the engine still wants to go higher. The original K-code engines used slightly larger rod bolts for a reason. Like baddog said, successful 350Z hunting can be done with a 289, but not with unmodified OE heads and a stock-ish rebuild.

Likewise, the car has had 42 years in which the gears (or even the whole axle) could have been swapped - for any number of reasons (my thumbnail car has had three gear swaps, for three different reasons). Anyway, the only sure way to find out is to pull the diff cover and count teeth. Counting wheel vs driveshaft revolutions works reasonably well as a quick and un-messy substitute, though the actual procedure differs a little between having an open diff or a limited slip.


Norm

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+1 on the gears

 

Well, like I said the plan is a start, I'm not expecting to get this done overnight.

anyway thanks for the help guys