I believe your 8x12 lathe is just like the 9X20 lathes and the chuck mounts with a threaded back plate. If so you can buy the chuck from any where and then buy the back plate from LMS. When you buy a new chuck and back plate you have to make a final cut on the back plate to make it match the chuck. It so all you have to do is buy a chuck with a PLAIN BACK and your good to go.
Here is one I found on E-Bay with a buy it now for $39.00 and $10.00 to ship.
4-JAW-INDEPENDENT-PLAIN-BACK-LATHE-CHUCK-HARDENED_W0QQcmdZViewItemQQ_trkparmsZ65Q3a12Q7c66Q3a2Q7c39Q3a1Q7c72Q3a1205Q7c240Q3a1318Q7c301Q3a1Q7c293Q3a1Q7c294Q3a50QQ_trksidZp3286Q2ec0Q2em14QQhashZitem51892dfdbbQQitemZ350193843643QQptZBIQ5fToolQ5fWorkQ5fHoldingQQsalenotsupported[/URL]
The same seller also offers a 5" chuck for $55.00. I wouldn't go any bigger for your lathe than the 5".
LMS wants $80.00 plus shipping for their 4" four jaw chuck.
This is the back plate you will probably need. You will have to check your thread first and make sure it's metric because some have an english thread.
http://www.littlemachineshop.com/pro...ry=-1110836144
As for the quick change tool post you can look for size AXA or 100, I believe they are the same size. You may have to cut down your tool post a little or the tool holders to make all of your tooling able to fit your lathe. There are several posts about this so do a search and check it out.
Dale P.