Well as I don't speak about street racing I will move on to your other comments. You can do just a rear gear swap opposed to a whole new rear change. Granny's speed shop offers a whole Ford 8.8 rear kit (suspension, rear & axels ect.)
I will assume that by staying carb'd you will most likely be doing a blow through system. I personally have little experience dealing with a carb'd turbo rotary, so I will leave this to someone else.
No you don't have to premix. Your motor should have an OMP "oil metering pump" which is there to supply oil to the chamber. In the event that someone has removed the OMP then yes you will need to premix. Some people premix with the OMP & there is this form Rotary Aviation
http://www.rotaryaviation.com/oil_in...p_adaptors.htm
The OMP is found on the front cover should have brittle lines attached to it.