i got the conversion for the low side port on the compressor and charged it last year. i cant find the high side port anywhere on this truck and i think i have a blockage in the line. the high side port would be helpful in diagnosis

 

The high side port should either be on the compressor or on the high side line just off the compressor.

 

Should be on the compressor or the outlet fitting from the compressor. On my 88, it's right next to the engine block so can be a finger burner if you're not careful.