The 337 is very underappreciated from a performance standpoint.  Remember, at the time, the 337 was competing directly against the OHV Cad 331 and was very comparable in power output (154 hp vs 160) and torque (265 ft-lbs vs. 292 ft-lbs).  That said, there is lots of room to improve.  I would start by studying the Harley Davidson KR engine.  Harley coaxed 60+ hp out of 45 ci in order to exploit a loop hole in the flat track rules at the time that gave flatheads a LARGE displacement advantage.  HD achieved this incredible 1.333 hp/ci with only 6:1 compression.  This would be perfect for a highly boosted application.  Imagine a 337 Lincoln with this same hp/ci ratio would produce 450 Hp!  The other place to look would be to get ahold of Rick Schnell up in Anoka.  He has the word's quickest flathead powered dragster.  The "Slider" is a 950 Hp+ Nitro huffing FED.  Obviously Nitromethane and a 4-71 blower will cover up a lot of sins, but I guarantee you Rick has a few flathead tricks up his sleeve.



https://www.youtube.com/watch?v=9-OXWC7Ufv4