Pretty much the title. How much power can you get out of a 337, the Big Block Flathead.
The Big Block Ford V8 Flathead - Route 66 Hot Rod High
That link (if it works for you) explains that "The 337 has a stock stroke of 4.375" and a rod diameter of 2.4". The rod journals can be offset ground down to small block chevy diameter of 2.1" resulting in a 4.675" stroke for 360 cid using a stock bore. Combined with a 3.6875" bore, you would have a 400 CID monster!" 399.42ci is more exact, but whatever.
What could you do with that, a cam, a huge 14-71 blower with matching intercooler, twin carbs. You know, all that fancy stuff.
250hp? 275? Or is that an overestimation?

...I don't know a lot about flatheads, except for that they're not good for making much power and that they're cool for classic hot rods.
I don't have a motor, or anything to put it in. I just want numbers.

 

Well, here's a start. I don't know which block gets the most favor. This is from '06, just after a big batch of French blocks were cut loose. (France used the flatty in military stuff into the '90s)

This'll get you going:

https://www.hotrod.com/articles/hdrp...athead-engine/

According to what you posted, there are no speed parts for the big guy.

Get a 3D printer that works in aluminum and steel, and you'll be good.

 

A 3D printer that works in aluminum and steel.
I bet that'll be cheap!
From what I've heard, the French blocks are the most common, of late.