I'd be interested in what backspace you are using. I've though about Buick rallys on my 87 T since I can never decide on any custom wheels I like. I still have 15 inch wheels left over from the 69 Skylark I had. I'll be running 235's up front and 245's in the rear. The guys on the V8 board have used McWheels in Iowa for custom wheel work.
The fronts are 15x7 with 3.75" rear backspacing