Starting when hot problem

I have a truck w/plow and I have a problem with starting it after it is warm/hot. The truck starts fine when it's cold but when it warms up sometimes it will start running a little rough and all the time if I shut it off then or it stalls then I don't have any response from the ignition or sometime I get a clicking sound like if I had a dead battery. I've replaced battery, alternator(upgraded to 100 amp), coil, distributor rotor and cap, starter, ground strap, plugs and plug wires. Still I have this problem. Now the other day I was using the plow and after a while I lost use of the plow movement after using it for about an hour so I shut the truck off and I tried to start it again and I had no response when I turned the key. So I let it sit for about 1 hour and then I tried starting it again and the truck started (a little harder than normal) and when I tried the plow movement it worked also. So I shut it off after about 15 minutes and tried to start it again and I all as I got was clicking noise. The next day it started fine again when it was cold. Please help I don't want to put anymore unnessacery money into this truck I just want to fix the problem and all my ideas are exhausted. By the way the heater don't work and when I try to turn it on the voltage gauge drops. I haven't turn it on since a couple of months ago when I found out it didn't work. I don't think this has anything to do with my major problem but I want to give all the info I can hoping that someone can help me. Thank you so much Danny