Chris,
Did you and your pal find all of the Stuart tank parts that you needed?
I see a pair of Caddy flatheads for sale on eBay as " Cadillac Tank engine's- WW2 early 1940's (2) each Item number: 180009706723 ".
http://cgi.ebay.com/ebaymotors/Cadil...spagenameZWDVW
better get them while they are hot ...
Stewart