Honestly,unless your making big,big power moving in the springs and mini tubbing isnt needed. With a nasty 450 h.p small block Id go with a home made set of caltracs,and yes they are simple to make. Require a welder,or a friend that can weld but pretty easy. If you can measure and cut metal,and get it welded,no problem. Otherwise,you may need to go old school with some ss springs or a pinion snubber. As for the tires,I'm not sure what will fit in the wheel wells on a sbp rim. Are you using the stock ralley wheel?
If your interested in the caltracs,I can email you some plans....