Suggestions on flathead choice

[RGC1]

Hi. I recently picked up a 34 fordor with a partial flathead thought to be a 34 block which I think is at max bore ……..if I was to pick or build a new flathead for the car that I whatted to pretty a few serious road miles on at times for a couple years. What would you suggest ?……….go find a 49-53 era flathead ? ….or 37 era and up ……pretty open
Thanks in advance