'48 Flathead RPM?
 

I have a '41 11t with a '48 flathead V8. I am going to re-gear the rear end, but I am not sure what rpm these engines like to run at going about 55-60 mph. With that info I can determine what rear end ratio I will use. Any information would be appreciated.

No Info!
 

What is real amazing to me, is that this post has only been up for a day and over 50 people have viewed it. But what is more amazing is that it is posted in the Flathead V8 section and nobody has an answer to what you would think would be a fairly easy question to answer...........

I read your post, but didn't know what a 11t was so moved on figuring somebody else would and could help you.

I take it you're running a 1 1/2 ton truck. The 59A engine is capable of revving pretty high. I'd say just under 3,000 continuous although they're happier in the 2,500 range. I know a lot of farmers in my home town that ran them for years and they were red-lined a lot and took it reasonably well. Of course the average was probably in the 45 mph range when they were on a level road with a full load of grain. I might add that the vast majority of those trucks were running 2 spd axles. If you were running a single speed I don't know if they even offered a ratio to get the speeds you want; they tended to be a stump puller. I think with a 2 spd you can get ratios as high as 5 to 1 in high range. With 20 inch tires you should be able to hit the speed(s) you want.
I hope this helps you out.
GMS

I can tell you from my experience if it helps. I have a 51 ford f6. I am running a stock 8ba with electronic ignition, dual exhausts and a k&n filter. 2 spd axle is 5.83 on the high side. I added a 3 spd brown lipe with a .72 OD. 2500 rpm at about 65 is all she will pull unless I have a strong tail wind. in direct loaded down I can hit 50 mph at about 2800-3000 rpm.