[Roadsters] New Transmission in, now a few questions

[Hoon Kim]

I finally got around to getting a working transmission into my  
roadster. Now I have a few questions.

I have a 4 speed tranny for a early 1600. Now that the transmission  
works, my speedo is working again. However it seems to be going very  
fast. If I am traveling at 40 mph, it will say 60 or so. Is this a  
matter of calibrating the speedo?

In that same regard, my trip meter is working again. If the speedo is  
not accurate, then would the trip meter/odometer also clock in more  
milage than real milage?

Last question, since my gas gauge doesn't work, if things were running  
smoothly (which they are) how many miles should I be able to go with  
average city milage on a full tank before I should fill up again using  
the trip meter?

Thanks again to the wonderful collective wisdom.

Hoon