[DeTomaso] Suspension geometry guru question

[John Bentley (jab)]

I'm struggling with finding a set of steel wheels to replace my clones
just for track/ORR.
 
Question: If I take off my 335/35-17 rears and want to replace with a
narrower tire (since I can't find a 11x17 steel wheel with a 6.5 inch
backspace) and keep the center of the tire tread in the same place, can
I just get a 2-inch narrower tire/wheel and replace with a wheel that
has a 1-inch less backspace?
 
What tire/wheel combination has the best chance of keeping the alignment
the same?  I'm more concerned with alignment issues than the looks of
the tire being an inch further inside the wheelwell/fender.
 
JB