Yes this thread is going sideways. J Rob, what is your idea of good mileage with the 340 you talk about? I get 20 with my 318 2 barrel Swinger and 19 with my 4 barrel 273. The teen has about 50,000 miles on it and the 273 is fairly fresh with about 10,000 so neither are worn out. You always hear stories of old C bodies with 383's getting close to 20. 2 barrel I'm sure and with a 2.... rear gear as well. Just curious what your expectations are.