Super Stock spring info needed !

I always preferred solid bushing up front & poly or rubber in back. For racing only, you want to minimize deflection. Similar situation with motor mounts, but keeping the trans mount poly or rubber to minimize binding & cracking anything. Just like frame connectors and roll bars - minimizing flex helps the car move quicker instead of having wasted energy and motion within the car. But nothing wrong with using poly or rubber up front, especially if it's not a race-only application.