It is a 134 specific Block valve... which includes a thermosyphoning valve and the regular tx valve..... this is not an easy item to reach and get the four lines attached to it off...I think I have seen a special ' holder' to be used to hold it ...
I think Larry and I agree on adding an inline filter upstream of the compressor when redoing an entire system... easy time to do it....and good safety factor...
Are you changing to a paralell condensor ? And upgrading your aux fan to one of those Italian ones ?