i have been interested in the extensive turbocharging experiments performed on Studebaker Champion sixes -- an engine even smaller than your Gnash, and a flathead to boot! See

http://www.studebakerdriversclub.com/documents/TurbochargingtheChampflatheadsix.pdf

i don't think i'll do this, but it is fascinating. On the basically stock Champ they recommend a Chrysler 2.2 TO-3 or a Buick Regal TO-4. That might get you started. Since you have demonstrated some gifts for this kind of ingenious engineering, i'm going to be watching what you do with great interest.

God's Peace to you.

d
Inliner #1450