what is the easiest way to run a dedicated "KEY ON" circut. I need to run my electric choke and tach with a key on but the rats nest under my dash is a winter job when i put a new harness in. any ideas how to run a seperate KEY ON circut temperary.  

What kind of alternator and starter are you using (I guess based on engine type)?  I've "temporarily" ran my electric choke wire off the starter solenoid on my '67 T-bird. The real fix would be off one of the terminals on the backside of the alternator (external regulator). I don't remember which terminal to use at the moment but I know there is one that becomes hot when the key is turned on or only when the engine is running. As for the tach... you will have to look for either a fuse or circuit breaker to tie into (depending on the vehicle, which is important to know...). If it is also to be temporary tap into the feed going to the radio on the + side and make sure you have a good ground.  It isn't ideal but would work for the short term.  

*Of course it just might be easier to run a toggle switch with a fuse right off the battery or alternator....