we put these on my buddies truck, '98 12v. was set at around 550hp at first. blew 3 head gaskets in 2 weeks. the second 2 were with studs.. we had to turn it down to around 400hp to get it to hold together. of course 12v's are a different animal compaired to cr's. these are strickly for towing and do a good job at that but are not made for anything more performance oriented.. but thats why they are advertised as towing twins right.. and thats what you asked about so ill leave my opinions out of it.