New Holley 1920 Needed

hi and hello:

great forum...great people..great knowledge. This forum saved me so many times. Now in need of a carb for my 1968 Dodge Dart 270.

carb is a Holly 1- bbl model 1920. Book shows R-3919-A, R-3921-A, R-3920-A, R-3922-A. Don't know what I have so where can I get a replacement w/ ethanol parts installed??? Who is a good carb rebuild specialist? Should I buy manufactured at $300 from NAPA?? My cam steps are completely worn and lots of twists in linkage...guy before was a klutz!!!

Many thx for advice/comments/recommendations. Long live 1968 Dodge Darts!