[truckin 79]

I have replaced the heater core in truck 2 years back. It was smaller and aluminum not brass that I bought from parts store. The heat in my truck gets warm but never hot. It is warm enough to defrost windshield but I thought with such a small cab it should get hot. I have a four core radiator and so temp only rises to the first mark on gauge not half. I am worried on those rare occasions when the temp drops to 0 or a little below here in CO
The second question is spare tire removal. I am getting tires changed and want to get a different tire on spare. I do not have the slide out tire just the standard type. I have not messed with it before, the spare tire on there now is like Christmas story spare. My spare is only a spare in the academic sense, it is round and once made of rubber with tread. Is it just as simple as unscrewing the nut with the eyelet and the taking spare out? Does the spare tire cross bar just fall to the ground or swing to the side? Is rim secured by a bolt or but that might be rusted?
Thanks in advance