I talked to my engine builder today. He said I have a 3.4 final  drive but with an overdrive primary gear, giving an effective ratio of 3.3:1 and that should give me 70mph @ 4000 rpm. 

Ill cross reference that with [//guessworks.uk/Tech/ratio.htm] and work out my redline speeds in 1st through 3rd. Thanks everyone for your help!

Email is correct. Thank you very much!

BTW, I figured out I have a 3.44 ratio by using a GPS app on my phone and recording the RPM in 4th at 60 MPH, which is about 3700.  I cruise on I-5 between 65 and 70 to keep from getting run off the road, which is about 4000-4300 RPM.

My speed reads about 10 MPH fast on the FWY.

Is your email correct?  I can send you a spreadsheet I created.

Robb

I think 3.3 is sort of possible by using one of the economy input gears on the first motion shaft or the economy primary gear with a 3.44 cwp.

Yeah, I think so. It's a Quaife LSD. My build sheet says it 3.31. I suppose it could be a typo. Thanks Malsal, Guessworks is just what I was looking for. [//guessworks.uk/Tech/ratio.htm] 

3.3:1?

Are you sure you have a 3.3 FD ? I would think you may have a 3.1 or a 3.4. A 3.1 or 2.9 or 2.76 seem to be the most desireable depending on the terrain where you live whether you want to cruise or go fast up to 70 mph. Also it depends on the engine you are using, the lower the ratio the less revs you turn in 4th gear.
Go to guessworks website in the UK and you can figure out the ratios there.

3.3:1?

Until I can get my tach working properly, I'd like to know how to calculate RPM vs. MPH ratios; specifically, what is my RPM at 65 MPH in 4th gear? Additionally, what is my MPH @ 6k RPM in 1st, 2nd, 3rd and 4th gear?

I have a 3.3:1 dif running 10" wheels w/ Yokohama 030s. If you're not familiar with the Yokos, they have a standard to slightly high profile sidewall. I can provide their circumference if somebody really wants to do the math, but I'm hoping there's a simplified table I can refer to. I found this thread on the forum that hints at some speeds vs. RPM but it's not very relevant to my particular circumstances [//www.minimania.com/msgThread/113703/1/1/Max_RPM_for_your_Mini_with_no_harm].

BTW: is a 3.3:1 dif considered an overdrive? Thanks!