A conversion neck is one that can convert an instrument from one scale length to another with no other modification. A common conversion is 34" to 32". By overhanging the 20th fret, or leaving it off, you can use the stock bridge location on the body, just adjust for intonation. Such a neck will work on any standard bass body. A conversion from 34" to 30" requires overhanging two frets, or losing one or both.
This is what a pound and a half of sawdust looks like. You'd be surprised how fast you can make it. This little vacuum, set up to be ultra-convenient, is worth its weight in gold. The vacuum is basically integrated into the workbench, so it is always handy. Both belt sanders have quick hookups.