Caroline, I have my 319w in treadle and it is my go to machine. I do a lot of piecing with mine, mending, whatever needs to be done because that machine is always out and ready to go! The 319 is a really easy machine to work with. The only difference between the 319 and your 306 is the stitches. The 319 has some built in cam stitches, where your 306 does not. Otherwise they are the same machine as Candace said. The 'L' bobbins are available from Sew Classic as are the needles - I am pretty sure that is where I got mine![ATTACH=CONFIG]383246[/ATTACH]
Nancy