88 dakota gets hot

I am wondering if I may have not done the proper things necessary when I changed the r12 to 134a . I read a thread in a forum the guy was explaining about the flow of the r12 system in first gen dakota is completely diff than the 134 and if you convert it the compressor doesn't get enough oil with it converted and won't hold up. And the one summer that it did work it was extremely cold and I am no a/c guru and my philosophy is if the compressor dies replace it all and start fresh and that has always worked for me but in this case I'm starting with a design flaw and I wonder if that might have caused the core to overheat? Cause I never heard of 134 getting colder than 12 and seams that if it gets colder wouldn't it also get hotter ?? I wish I would have gotten a temp reading from it before it died. What do ya'll think about this theory ???