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The 700R4 is not an electronically controlled trans. It uses the TV cable to help control it's operation. The other option as TJ mentioned is the NV3500 or NV4500. The NV3500 does not have the 'granny' low 1st gear as the NV4500 does. Both are setup with a hydraulic clutch, but the NV4500 can be converted to a mechanical clutch with the purchase of an aftermarket bellhousing from Advanced Adapters. The NV3500 can not be converted.
You can use your existing 15" wheels if they are disc brake compatible.