92 Gmc 5.7l 350 Stock

[Southern Comfort]

As the title says I have a 92 GMC 1500 2wd with the RPO L05 VIN K 5.7L completely stock with approximately 87,000 miles. My question pertains to the newer oils with less ZDDP. I have asked around a good bit with conflicting answers to whether or not my stock 350 has flat tappet or roller lifters factory. Should I be using any type or additive with more ZDDP? I have been told yes I should be and other have told me no that the oil you buy today if just fine. Some have even told me that if it came with a catalytic converter then it had roller lifters since the higher levels of ZDDP affect the long term life of the converter. This truck does still have the converter in place. I have a 86 El Camino that came stock with catalytic converter and the RPO LG4 5.0L and almost sure it has flat tappet lifters so that statement does not seem true.

If anyone knows for sure what these trucks came with flat tappet or roller lifters and if it would be best to use additional ZDDP additives the advice and insight would be very much appreciated.

[Jsdirt]

I never ran anything fancy in my '94 K1500, but this oil here definitely has enough zinc for vehicle with flat-tappets:

 

http://www.amsoil.com/storefront/zrt.aspx

[GMstrong]

flat tappet.Roller blocks were only in car the gm trucks didnt get roller block until 96