G/V overdrive and 700R4 vs. TCI 6 speed auto

[Z POPPY]

In need of some feedback. Going with a large built SBC and a built 700R4, 1964 c10. Thinking about going with a gearvendor O/D behind the 700R4. Claims of 10-15% MPH with gearvendors (about 2.25 mile more per gallon). G/V and 700R4 requires no shift programming and gets a .55 final trans ratio. Can handle what I am building. A friend suggested the new O/D from the general a 6L80E. It has a final trans ratio of .75 with 6 foward gears and TCI builds a monster version the generals. Adjustable shift points, full manual shifting with paddle shifter and would cost the same as a 700R4 and the G/V unit. It is just a matter of time before gas returns to $5 bucks a gallon. Other friends said keep it simple, built 700R4 and add G/V later if I still want it. Check out these pages and let me know what ya think.

http://www.gearvendors.com/hrgm4s.html

http://www.tciauto.com/Products/6x/