CAN YOU HELP ME? PLEASE!!!!!!!!

My car has been sitting for a while but I just put in a rebuilt T5 transmission for my 90 mustang, it was sittin cus my other trans blew...after getting it all together, I go and try to start my car...it wont turn over, fuel pump comes on but when the key is turn nothing works. I hook my battery up to a charger and tried again, but once again nothing worked. I already put a new starter on the car, so I just pulled it out and put it in again, still nothing happened. So I try a screw driver on the cillinoid, and whoa it starts up. So I am thinking it is either that starter/clutch interlock switch under the dash right up against the clutch pedal itself, or the actual starter switch on the stearing column. I looked to see if the clutch switch was pushed in when the clutch was held down, it was, and i tried to turn the key and nothing happened. I was told there was a way to by-pass that switch by taking the 2 plugs out of the switch and connecting them, but that didnt work for me either. So i took the 2 plugs to see if there was any juice running to them, but my test light didnt light up.no juice. So plug that all back in and look toward the actual starter switch. I had another one from my old mustang. I took it off that steering column and plugged it into my car, to see if it would work. and still nothing works. I dont know what to do about this...Would it have anything to do with my STARTER? or is it somethign with this new transmission?......any ideas would really help me out

Now to the next problem I have now....For the summer i take out my thermostat, now for winter I went to put a new one in. And I can not get any hot air blowing. Theres hoses are hot going into the heatercore and coming out....but I can not get any warm air to blow...I did once for a couple seconds, but that was it. What the heck is wrong with this I dont know...anyone got any ideas?