i need the gasket that goes in between the tranny adapter, and my NP241. the tranny is a 4L60. this is on my 91 K5. NOBODY has this gasket. neither NAPA or O'Rilley's distribution centers even knows what the hell i'm talking about. it's not in the fel-pro book. does GM have it? or can i just use some high temp RTV?? i'm hesitant to use RTV, i don't want it to leak, and, i don't want any RTV getting in the tcase. what should i dO? it's a big round circle, with 6 equi-distant bolt holes.