MPLAB X IDE version 5.35 is highly sought after because it is the to include and support the MPASM assembler . Starting with version 5.40, the IDE became a 64-bit-only application and dropped MPASM in favor of the newer pic-as toolchain. How to Download MPLAB X IDE v5.35
The story of MPLAB X v5.35 is essentially the "last stand" of classic 8-bit assembly programming. mplab 5.35 download