1995 Celica ST 205 JDM Speedometer Conversion

[RobsGT4]

Cheers you glorious people. In depth question here (yes I have searched but not found the answers I am looking for)... I am currently living in Japan, and have picked up a 1995 GT4, completely stock other than aftermarket wheels. I will eventually be moving back to the USA at some point, and would like to be able to monitor my speed accordingly. Looking for weigh in on several options, and the feasibility and pros/cons of each. 

1) I guess this is the cheapest method, of the speedometer converter that you wire in. Yes it's cheap, yes it bypasses the speed limiter, but not sure I want to fiddle with systems like that and induce another possible point of failure. Seems to be a hack approach to fixing the issue. Are these really any good? 

2) if I were to replace the speedometer sensor unit on the transmission for a UK spec version, would that alter the speedometer output from kph to mph? Would it bypass the speed limiter? What is that part number, as I am having a time locating it. Would I also need to replace the speedometer itself while I'm in there? 

3) Most expensive version of life might be new ECU like the Link G4, which is an eventuality anyways. I know you can remove the speed limiter. Can you modify the speed outputs to the speedometer through this manner? 

4) Other options for converting to a MPH system and removing the speed limiter I haven't considered?