it all started a year and a half ago .My 07 1500 classic with the 4.3 started skipping, check engine light came on ,and I said " well it ain't flashing so i'll worry about it later " . Turns out it was my thermostat stuck open . during that time it overheated once almost to 250 , from that point on the skipping started .I changed all the typical stuff with no result . took it to the dealer and they said the right bank o2 sensors were bad and the cats needed to be replaced . I asked them what caused the cats to go bad ? he didn't know ,but would dig deeper to find out . block test reviled blown head gasket ,and due to having 247000 miles on it they wouldn't fix it just replace the engine (4800 +) no thanks . I bought a used engine for 500 out of a 05 ,and within a few months the mil was flashing . auto zone gave me 17 codes to check out .I got everything fixed the truck was running better ,but still had a dead miss and stumbling .p300 is all that's left ,I took it to the dealer ,and they tell me that there are 3 injectors that are stuck at wide open position ,1 is stuck closed and 1 is barely working ,cylinder 5 is the only one working . So I have my old spider injection from my original engine . I'm pretty sure it works ,but who knows for how long . I just don't want to dump 400 $ in it and it still be skipping . either way I'm dead in the water right now it seems nobody has a gasket kit for it so it will be Monday before I can get it . If those injectors don't work and have to be replaced is there difference between the rebuilt or new ones..... as far as reliability goes ?