Running cold,and heavy vibration/and brakes ?

1)well after installing new radiator my overheating probelms went away,but now the darn things runs too cool??
the gauge works,(stock) and when i was flushing the system the gauge would read to the R on the N_O_R_M_A_L part then drop a little....now even after traffic and anything it stays at the _A_...??? the t-stat is opening and everything is functioning? it has the 190 t stat and it never gets that hot then comes down, it just starts at _0_ and then it goes to the A(never higher)....it was not doing that when flushing, it would go up to the _R_ an them come down to a little above the _A_.....(the rear end was jacked up when doing the flush)


2)also my other question is,after about 5k the motor really vibrates, not like solid motor mounts vibrates(which i just installed),but like about to blow up vibrates....
got new tires 245 45 17,and i cannot rip 2nd from a roll or chirp anything, i think it has something to do with my clutch king cobra and pressure plate(centerforce stage 2) or would this allow for greater hold and therefore greater tire rips??... could improper clutch adjustment be holding me back..or oil starvation in the powerband,oil pressure goes up when in the upper powerband..stock gauage reads at the _R_...and aftermarket reads 30psi cold, 40psi warm idle and 50-52psi in powerband...just want to make sure im not blowing this thing up??

3)my other theory is brakes, i notice every time the car sits for a day and i put it in gear and move it the car has to brake free and i hear the drums bust loose(slightly normal i suppose) but i did replace a leaking brake cylinder and noticed that with the wheels on and the car in 1st-rev then to neutral the wheels only spin freely for like 2-3 seconds before gravity and im sure improper drum adjustment nearly stops them... could my rear brakes need adjusting??

i guess this could be a tech topic as well,please move if needed
thanks