Do you think you'd have the brake/ball joint clearance to go with a 4.75" backspace on a 15 up front? I haven't tried it, but I know that the limit for clearance on a 15" rim is pretty close to that...
If that's the goal then get the tubular control arms unless they will put you in a racing class you don't want to be in. You will want the additional negative camber and positive caster you can get with them, and not have to worry about trading one for the other to get the alignment specs equal. With offset bushings and stock UCA's there's less range, and you may have to compromise on one alignment setting to get the other to the point that you don't get what you want in some places.
If that's the only use of the car, you'll want to dial in more negative camber as well as it will help with traction on that surface. If it's still going to be a street going car you'll want to stay at around -1° camber, otherwise you will start to see camber wear on the tires. But I'd be looking for -1° camber (or more for race only), +5° or more caster (which also adds more camber on turns), and 1/16" toe in. And you'll need at least non-adjustable tubular UCA's to get that. The gen I SPC UCA's I run from @BergmanAutoCraft would make those settings easy to get.
