1950 Shoebox Flathead questions

I've been working on my Shoebox for the past 2 months and driving it daily. Has a great running 239 in it with the 3 speed and stock rear. I drive it on the freeway about 12 miles everyday. My questions are,

What is a safe RPM range to take it to in 3rd?

And what are the gear size in the rear end?

I've searched and couldn't find anything from the HAMB or google. Thank you!

 

I also forgot to mention it's an all stock on the motor.

 

I was told to keep mine around 2600 RPM and it won't hurt it.

 

See the 239 in mine seems to run smoothest at 3000 RPM. But I dont know if that's bad on the motor. Seems to be at 60 -65 MPH around there.

 

Std. on the 49-51 is 3.73 Change to fordamatic will require changing complete housing.
A friend changed his to a Maverick, by moving spring pads.

 

I drove my former almost stock 239 (max-1 cam, offy heads, 2 97's) 3000rpm on the freeway without any problems.

 

ttt for the night crew

 

Huh? I have a '51 (no overdrive) and it has a 3.55. I gotta believe that the alternative thrid members are interchangeable (3.55, 3.73, 4.11). Correct me if I'm wrong.

BTW, I took my car from the twin cities to Chicago for a car show about 20 years ago, and had no problem holding 65mph on the freeway on the way down. I don't have a tach, but it didn't seem the engine was working to hard at any time.

 

My 50 flattie is bored 3 5/16 and stroked to 4". Mild cam, offy heads and 2 dueces with a C-4. I first ran the stock rear (from a stick car). I ran 3400 rpm on hiway at about 65mph. Didn't have much power to pass at that speed. Was told by a flatty "expert" that 2400 was more reasonable for a flatty. I changed rears to a Maverick 8" w/3.00 gears. Dropped about 900 rpms, now when I run at 65 mph, I have some power left to pass.

 

When you decide to swap a Maverick rearend be sure its out of a V8 car and you'll end up with the same 5 lug wheel pattern.

 

Flatheads are probably most comfortable from 2-3K RPM, regardless of speed. How you set up your rear gear, tire size, what tranny, etc, is entirely dependent on how you want to use the car. For me, I run 5-speeds behind my flatties since I like to go long distance, usually with a 3:50 gearset and a 29-31" tire. Depending on my specific combo, I'm usually running 2500 at around 70MPH with plenty to pass and more gears to downshift to if I need more. Gas mileage is usually around 18-22 depending on terrain (hills or flat). This also all matches up well to what custonrod48 has said for your automatic combo.