The Lowe Conversion STC paperwork, along with detailed instructions and parts lists costs $500 USD.
If you want to do the conversion yourself, (or have it done for you,) all the parts needed
can be supplied by a 'donor' Cessna 120/140 or 140A. If you don't want to use a donor plane,
you can look around and find all the parts needed from different sources.
A list of parts needed is in the STC paperwork.
If you already have a Cessna 150 Fuselage, you must first buy the STC for $500. Then you can bring it to David and he will do the conversion and supply all the conversion parts for $8,000. USD (total $8500).