It's got tons of 289 FIA/USRRC cues; under car side exhaust, forward roll bar brace, fuel filler location, small front air inlet, cut back rear door edge.
Like this CSX 2431, 1965 USRRC @ Riverside pix:
[EDIT: corrected picture...]
it could be CSX2430 (or a copy of same, the wheels are not proper, as these Shelby American Collection photos show):
http://www.shelbyamericancollection....n/csx2430.html