Just got my exhaust manifolds back from machine shop. Wanting to bolt on but wanted to ask what rtv have people used that they can vouch for. I was considering 3 different ones. All permatex. High temp red I think is good for 650 degrees, ultra copper is about 700 and they also have a "muffler sealant" rated for 2000. Anyone ever use these or another product they can recommend? And before anyone tells me to use gaskets, I can't. Motor is a 78 and they don't make any performance gaskets for this motor. Just ones that have a reputation for blowing out which is why I am going gasketless and had manifolds machined.