Finding instant center on a 1960 Impala

[11thhourfabrication]

I am having some problems trying to find the instant center on my 1960 chevy sedan delivery (same as Impala). After plotting the points as best I could with the sheetmetal still on the car the lines for the upper and lower control arms do not converge but go off in opposite directions. I am using Global West UCA and LCA and a CPP dropped stock style spindle. Does anybody have any suggestions.

Thanks in advance