I had a 2sp in my bird and my wagon. Good strong tranny. Cool factor was it could go to 55 mph in 1st gear! Therefore, a weeee bit slower. Gas milage is great, if you don't try and gun it all the time so just like everything else mpg determined by the driver.
Keep the 2sp if it's a survivor or go with TH400 3sp (if you want stock), 4sp if you think your faster than an automatic with shift kit.
Engine Test Stand Playlist: https://www.youtube.com/playlist?list=PLwoxyUwptUcdqEb-o2ArqyiUaHW0G_C88 restoring my 1968 Firebird 400 HO convertible (Firedawg) 1965 Pontiac Catalina Safari Wagon 389 TriPower (Catwagon) 1999 JD AWS LX Lawn tractor 17hp (my daily driver) 2006 Sequoia 2017 Murano (wife's car) 202? Electric car 203? 68 Firebird /w electric engine 2007 Bayliner 175 runabout /w 3.0L Mercuiser__________________________________________________________
