Five speeds and EFI

Hey folks how are you? Well I wanted to ask if any of you use your old mustang as a driver have you switched to EFI or an overdrive transmission? I want to start using my mustangs on my longer trips that I take on vacations but the problem for me has always been that on the freeway these cars basically just don't cut it. Rpm's are up way too high and gas is getting guzzled too rapidly and at $3 a gallon that's becoming an issue. I would imagine the t-5 tranny swap helps alot but what about changing the ring and pinion to more freeway friendly gears. Can that alone help very much? It seems like my Sister's '73 Grande cruises just fine at 70 mph and that's with a 302/c4. Any input would be greatly appreciated!

I put an AOD in my GT/CS, it has 389 rear end gears. The car hits about 2100 rpm at 75 to 80 on the Freeway. The AOD is great, and I 've had no problems. (I have 400+ HP in the car and 400+FPT) When I want to Hot Rod around, I drop it into 3rd and it will smoke the tires thru all the gears, if I keep my foot in it. Bluto ;D

I recently read of a owner of a Shelby GT-350 ('68?) which swapped out the 3.25:1 gears for a 3.00:1 set (which was the original ratio), and he achieved 23 mpg! He had a 4 speed, but it kinda gives you an idea as to what is possible with a well-tuned motor and keeping one's foot off the go-pedal.

[quote author=007bluto link=board=4;threadid=1616;start=0#msg9780 date=1114367134]
I put an AOD in my GT/CS, I have 400+ HP in the car and 400+FPT)
[/quote]

Bluto, did you use a stock AOD or did you have it gone through with shift kit etc.?
Could you post or send me a mail as to what steps you took and what you ran into that you didn't expect?
I'm keeping my eyes open for a good deal on one, I just haven't found it yet. It seems like a really good idea to me.
Thanks Bill

I have thought alot about this. A T5 and a set of taller gears. You get the best of both worlds. Low end monster torque, great cruising RPM's and not so worried about blowing up my Top loader or motor. Anyone did this manual?