Some 97 SLP cars had balanced driveshafts from SLP. I know my Firehawk lists it on the option sheet.

 

I'm pretty sure they were actually a different steel ds just for the LT4 cars, I know SLP used to sell them listed as "LT4 driveshafts" for like $300.00. They also used one on the "Grape of wrath" car in GMHTP.

 

OK, that would make sense. I know it is a steel unit (it's rusted), and it is balanced (no vibration and there are weights on it). I just figured they were an option on all 97 SLP cars, but they might have only been on the LT4s.